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Sökning: WFRF:(Salomé Pedro)

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1.
  • Edoff, Marika, 1965-, et al. (författare)
  • Ultrathin CIGS Solar Cells with Passivated and Highly Reflective Back Contacts – : Results from the ARCIGS-M Consortium
  • 2019
  • Ingår i: Proceedings of 36th European Photovoltaic Solar Energy Conference and Exhibition. ; , s. 597-600
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • In this work, we report results from the EU-funded project ARCIGS-M. The project started in 2016 and aims to reduce the use of indium and gallium by enabling the use of very thin Cu(In,Ga)Se2 (CIGS) layers while retaining high efficiency and developing innovative low-cost steel substrates as alternatives to glass. In the project, reflective layers containing TCO´s and silver have successfully been used to enhance the reflective properties of the rear contact. In addition, passivation layers based on alumina (Al2O3) deposited by atomic layer deposition (ALD) have been found to yield good passivation of the rear contact. Since the alumina layers are dielectric, perforation of these layers is necessary to provide adequate contacting. The design of the perforation patterns has been investigated by a combination of modeling and experimental verification by electron beam lithography. In parallel a nano-imprint lithography (NIL) process is further developed for scale-up and application in prototype modules. Advanced optoelectrical characterization supported by modeling is used to fill in the missing gaps in optical and electrical properties, regarding CIGS, interfaces and back contact materials.
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2.
  • Alberto, Helena, V, et al. (författare)
  • Characterization of the Interfacial Defect Layer in Chalcopyrite Solar Cells by Depth-Resolved Muon Spin Spectroscopy
  • 2022
  • Ingår i: Advanced Materials Interfaces. - : John Wiley & Sons. - 2196-7350. ; 9:19
  • Tidskriftsartikel (refereegranskat)abstract
    • As devices become smaller and more complex, the interfaces between adjacent materials become increasingly important and are often critical to device performance. An important research goal is to improve the interface between the absorber and the window layer by inserting buffer layers to adjust the transition. Depth-resolved studies are key for a fundamental understanding of the interface. In the present experiment, the interface between the chalcopyrite Cu(In,Ga)Se-2 absorber and various buffer layers are investigated using low-energy muon spin rotation (mu SR) spectroscopy. Depth resolution in the nm range is achieved by implanting the muons with different energies so that they stop at different depths in the sample. Near the interface, a region about 50 nm wide is detected where the lattice is more distorted than further inside the absorber. The distortion is attributed to the long-range strain field caused by defects. These measurements allow a quantification of the corresponding passivation effect of the buffer layer. Bath-deposited cadmium sulfide provides the best defect passivation in the near interface region, in contrast to the dry-deposited oxides, which have a much smaller effect. The experiment demonstrates the great potential of low energy mu SR spectroscopy for microscopic interfacial studies of multilayer systems.
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3.
  • Bose, Sourav, et al. (författare)
  • Optical Lithography Patterning of SiO2 Layers for Interface Passivation of Thin Film Solar Cells
  • 2018
  • Ingår i: Solar RRL. - : Wiley. - 2367-198X. ; 2:12
  • Tidskriftsartikel (refereegranskat)abstract
    • Ultrathin Cu(In,Ga)Se-2 solar cells are a promising way to reduce costs and to increase the electrical performance of thin film solar cells. An optical lithography process that can produce sub-micrometer contacts in a SiO2 passivation layer at the CIGS rear contact is developed in this work. Furthermore, an optimization of the patterning dimensions reveals constrains over the features sizes. High passivation areas of the rear contact are needed to passivate the CIGS interface so that high performing solar cells can be obtained. However, these dimensions should not be achieved by using long distances between the contacts as they lead to poor electrical performance due to poor carrier extraction. This study expands the choice of passivation materials already known for ultrathin solar cells and its fabrication techniques.
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4.
  • Cunha, Jose M., V, et al. (författare)
  • Decoupling of Optical and Electrical Properties of Rear Contact CIGS Solar Cells
  • 2019
  • Ingår i: IEEE Journal of Photovoltaics. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-3381 .- 2156-3403. ; 9:6, s. 1857-1862
  • Tidskriftsartikel (refereegranskat)abstract
    • A novel architecture that comprises rear interface passivation and increased rear optical reflection is presented with the following advantages: i) enhanced optical reflection is achieved by the deposition of a metallic layer over the Mo rear contact; ii) improved interface qualitywithCIGS by adding a sputteredAl 2O 3 layer over the metallic layer; and, iii) optimal ohmic electrical contact ensured by rear-openings refilling with a second layer of Mo as generally observed from the growth of CIGS on Mo. Hence, a decoupling between the electrical function and the optical purpose of the rear substrate is achieved. We present in detail the manufacturing procedure of such type of architecture together with its benefits and caveats. A preliminary analysis showing an architecture proof-of-concept is presented and discussed.
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5.
  • Cunha, Jose M. V., et al. (författare)
  • High-Performance and Industrially Viable Nanostructured SiOx Layers for Interface Passivation in Thin Film Solar Cells
  • 2021
  • Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 5:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Herein, it is demonstrated, by using industrial techniques, that a passivation layer with nanocontacts based on silicon oxide (SiOx) leads to significant improvements in the optoelectronical performance of ultrathin Cu(In,Ga)Se-2 (CIGS) solar cells. Two approaches are applied for contact patterning of the passivation layer: point contacts and line contacts. For two CIGS growth conditions, 550 and 500 degrees C, the SiOx passivation layer demonstrates positive passivation properties, which are supported by electrical simulations. Such positive effects lead to an increase in the light to power conversion efficiency value of 2.6% (absolute value) for passivated devices compared with a nonpassivated reference device. Strikingly, both passivation architectures present similar efficiency values. However, there is a trade-off between passivation effect and charge extraction, as demonstrated by the trade-off between open-circuit voltage (V-oc) and short-circuit current density (J(sc)) compared with fill factor (FF). For the first time, a fully industrial upscalable process combining SiOx as rear passivation layer deposited by chemical vapor deposition, with photolithography for line contacts, yields promising results toward high-performance and low-cost ultrathin CIGS solar cells with champion devices reaching efficiency values of 12%, demonstrating the potential of SiOx as a passivation material for energy conversion devices.
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6.
  • Cunha, José M. V., et al. (författare)
  • Understanding the AC Equivalent Circuit Response of Ultrathin Cu(In,Ga)Se2 Solar Cells
  • 2019
  • Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 9:5, s. 1442-1448
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper aims to study the ac electrical response of standard-thick, ultrathin, and passivated ultrathin Cu(In,Ga)Se 2 (CIGS) solar cells. Ultrathin CIGS is desired to reduce production costs of CIGS solar cells. Equivalent circuits for modeling the behavior of each type of solar cells in ac regime are based on admittance measurements. It is of the utmost importance to understand the ac electrical behavior of each device, as the electrical behavior of ultrathin and passivated ultrathin CIGS devices is yet to be fully understood. The analysis shows a simpler ac equivalent circuit for the ultrathin device without passivation layer, which might be explained by the lowered bulk recombination for thin-film CIGS solar cells when compared with reference thick ones. Moreover, it is observed an increase in shunt resistance for the passivated ultrathin device, which strengthens the importance of passivation for shunts mitigation when compared with unpassivated devices.
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7.
  • Fernandes, P. A., et al. (författare)
  • Thermodynamic pathway for the formation of SnSe and SnSe2 polycrystalline thin films by selenization of metal precursors
  • 2013
  • Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 15:47, s. 10278-10286
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, tin selenide thin films (SnSex) were grown on soda lime glass substrates by selenization of dc magnetron sputtered Sn metallic precursors. Selenization was performed at maximum temperatures in the range 300 degrees C to 570 degrees C. The thickness and the composition of the films were analysed using step profilometry and energy dispersive spectroscopy, respectively. The films were structurally and optically investigated by X-ray diffraction, Raman spectroscopy and optical transmittance and reflectance measurements. X-Ray diffraction patterns suggest that for temperatures between 300 degrees C and 470 degrees C, the films are composed of the hexagonal-SnSe2 phase. By increasing the temperature, the films selenized at maximum temperatures of 530 degrees C and 570 degrees C show orthorhombic-SnSe as the dominant phase with a preferential crystal orientation along the (400) crystallographic plane. Raman scattering analysis allowed the assignment of peaks at 119 cm(-1) and 185 cm(-1) to the hexagonal-SnSe2 phase and those at 108 cm(-1), 130 cm(-1) and 150 cm(-1) to the orthorhombic-SnSe phase. All samples presented traces of condensed amorphous Se with a characteristic Raman peak located at 255 cm(-1). From optical measurements, the estimated band gap energies for hexagonal-SnSe2 were close to 0.9 eV and 1.7 eV for indirect forbidden and direct transitions, respectively. The samples with the dominant orthorhombic-SnSe phase presented estimated band gap energies of 0.95 eV and 1.15 eV for indirect allowed and direct allowed transitions, respectively.
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8.
  • Ferrando, Carlos, et al. (författare)
  • Effects of oxygen on post-surgical infections during an individualised perioperative open-lung ventilatory strategy : a randomised controlled trial
  • 2020
  • Ingår i: British Journal of Anaesthesia. - : ELSEVIER SCI LTD. - 0007-0912 .- 1471-6771. ; 124:1, s. 110-120
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: We aimed to examine whether using a high fraction of inspired oxygen (FIO2) in the context of an individualised intra- and postoperative open-lung ventilation approach could decrease surgical site infection (SSI) in patients scheduled for abdominal surgery. Methods: We performed a multicentre, randomised controlled clinical trial in a network of 21 university hospitals from June 6, 2017 to July 19, 2018. Patients undergoing abdominal surgery were randomly assigned to receive a high (0.80) or conventional (0.3) FIO2 during the intraoperative period and during the first 3 postoperative hours. All patients were mechanically ventilated with an open-lung strategy, which included recruitment manoeuvres and individualised positive end-expiratory pressure for the best respiratory-system compliance, and individualised continuous postoperative airway pressure for adequate peripheral oxyhaemoglobin saturation. The primary outcome was the prevalence of SSI within the first 7 postoperative days. The secondary outcomes were composites of systemic complications, length of intensive care and hospital stay, and 6-month mortality. Results: We enrolled 740 subjects: 371 in the high FIO2 group and 369 in the low FIO2 group. Data from 717 subjects were available for final analysis. The rate of SSI during the first postoperative week did not differ between high (8.9%) and low (9.4%) FIO2 groups (relative risk [RR]: 0.94; 95% confidence interval [CI]: 0.59-1.50; P=0.90]). Secondary outcomes, such as atelectasis (7.7% vs 9.8%; RR: 0.77; 95% CI: 0.48-1.25; P=0.38) and myocardial ischaemia (0.6% [n=2] vs 0% [n=0]; P=0.47) did not differ between groups. Conclusions: An oxygenation strategy using high FIO2 compared with conventional FIO2 did not reduce postoperative SSIs in abdominal surgery. No differences in secondary outcomes or adverse events were found.
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9.
  • Fjällström, Viktor, et al. (författare)
  • Recovery After Potential-Induced Degradation of CuIn1-xGaxSe2 Solar Cells With CdS and Zn(O,S) Buffer Layers
  • 2015
  • Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 5:2, s. 664-669
  • Tidskriftsartikel (refereegranskat)abstract
    • This study deals with potential-induced degradation (PID) of Cu(In,Ga)Se-2-based solar cells and different approaches to subsequent recovery of efficiency. Three different recovery methods were studied: 1) etch recovery, 2) accelerated recovery, and 3) unaccelerated recovery. After being completely degraded, the solar cells with CdS buffer layers recovered their efficiencies at different rates, depending on the method which was used. On the other hand, if Zn(O,S) was used as a buffer layer instead of CdS, the recovery rate was close to zero. The buffer layer type clearly influenced the sodium distribution during PID stressing and recovery, as well as the possibilities for recovery of the electrical performance.
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10.
  • Frisk, Christopher, 1985-, et al. (författare)
  • Modeling Ga-profiles for Cu(In,Ga)Se2 thin film solar cells with varying defect density
  • 2013
  • Ingår i: 23rd International Photovoltaic Science and Engineering Conference; Taipei, Taiwan; October 28 - Nov 1, 2013.
  • Konferensbidrag (refereegranskat)abstract
    • The very best Cu(In,Ga)(S,Se)2 solar cells have a double graded band gap in the absorber, i.e. a notch profile, formed by varying the ratio of Ga to In. If this is a prerequisite or a consequence of high quality deposition methods is something yet of discussion. In this work we have constructed a high efficiency model (HE-T61) based on in-house state-of-the art Cu(In,Ga)Se2 solar cells, with efficiencies above 19 %, and investigated the role of the Ga-profile. Notch-type Ga-profiles have been compared with single graded profiles, and the influence of Ga-dependent defect distribution and metastable defects have been investigated showing that the optimum Ga-profile is dependent on such defect variations. It is also shown that within the HE-T61 model the optimized Ga-profile yields up to 3 % absolute efficiency gain, indicating that there is potential in band gap engineering.
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11.
  • Gomes, Daniel A, et al. (författare)
  • Impact of common rhythm disturbances on echocardiographic measurements and interpretation
  • 2022
  • Ingår i: Clinical Research in Cardiology. - : Springer Nature. - 1861-0684 .- 1861-0692. ; 111:12, s. 1301-1312
  • Tidskriftsartikel (refereegranskat)abstract
    • Transthoracic echocardiography (TTE) remains the workhorse of noninvasive cardiac imaging, allowing to easily obtain precise information on cardiac structure and function. Over time, Doppler interrogation of blood flow velocities, direction, and timing in several locations within the heart became the primary method for haemodynamic assessment, replacing cardiac catheterization in most clinical settings and providing valuable diagnostic and prognostic information on a wide spectrum of cardiac pathological processes. Abnormalities in heart rate, rhythm, and intracardiac electrical conduction are commonly encountered during the performance of echocardiographic studies. Up to now, only a modest attention has been given to the impact of these abnormalities on the reading and interpretation of echocardiographic examination and this assessment has not yet been carried out in a global and systematic way. Tachyarrhythmias, bradyarrhythmias and atrioventricular conduction disturbances influence cardiac structure and mechanics as well as Doppler flow patterns. For this reason, and to be able to avoid misinterpretation, echocardiographers must be aware of the consequences of these common rhythm disturbances on echocardiographic findings. This narrative review aims to describe the current knowledge on this topic, focusing on the expected mechanical effects and Doppler patterns observed on transthoracic echocardiography in patients with common rhythm (tachycardia and bradycardia, atrial flutter and fibrillation and ectopic beats) and conduction disturbances (namely, atrioventricular block).
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12.
  • Hultqvist, Adam, et al. (författare)
  • Performance of Cu(In,Ga)Se-2 solar cells using nominally alkali free glass substrates with varying coefficient of thermal expansion
  • 2013
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 114:9, s. 094501-
  • Tidskriftsartikel (refereegranskat)abstract
    • In this report, Cu(In,Ga)Se-2, CIGS, solar cell devices have been fabricated on nominally alkali free glasses with varying coefficients of thermal expansion (CTE) from 50 to 95* 10(-7)/degrees C. A layer of NaF deposited on top of the Mo was used to provide Na to the CIGS film. Increasing the glass CTE leads to a change of stress state of the solar cell stack as evidenced by measured changes of stress state of the Mo layer after CIGS deposition. The open circuit voltage, the short circuit current density, and the fill factors, for solar cells made on the various substrates, are all found to increase with CTE to a certain point. The median energy conversion efficiency values for 32 solar cells increases from 14.6% to the lowest CTE glass to 16.5% and 16.6%, respectively, for the two highest CTE glasses, which have CTE values closest to that of the soda lime glass. This is only slightly lower than the 17.0% median of soda lime glass reference devices. We propose a model where an increased defect density in the CIGS layer caused by thermal mismatch during cool-down is responsible for the lower efficiency for the low CTE glass substrates.
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13.
  • Kovacic, Milan, et al. (författare)
  • Light Management in Ultra-Thin Cu(In, Ga)Se2 Photovoltaic Devices
  • 2019
  • Ingår i: Proceedings of 36th European Photovoltaic Solar Energy Conference and Exhibition. - 3936338604 ; , s. 654-660
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Cu(In, Ga)Se2 (CIGS) solar cells exhibit high conversion efficiencies, with a recent record of 23.35 % on the cell level. However, an absorber thickness >1.8 m is required for efficient absorption of long-wavelength light. In order to minimize the material consumption (In, Ga and other elements) and to accelerate the fabrication process, further thinning down of CIGS absorber layer is important. One of the main challenges of ultra-thin absorber devices is to increase light absorption and consequently the photocurrent. We employ advanced optical simulations of ultra-thin (500 nm) CIGS devices in a PV module configuration, thus solar cell structure including encapsulation and front glass. Using simulations, we design and investigate different solutions for increased short circuit current, in particular (i) highly reflective back reflectors (BR), (ii) internal nano-textures and (iii) external textures by applying a light management foil. We show that any single solution (i, ii, iii) is not enough to compensate for the lower photocurrent, when thinning down (1800 nm -> 500 nm) the absorber layer. A combination of properly optimized internal or external textures and highly reflective back reflector is needed to reach, or even exceed (by ~3-5 %), the short circuit current of a standard thick (1800 nm) CIGS module structure.
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14.
  • Ledinek, Dorothea, et al. (författare)
  • Rear Contact Passivation for High Bandgap Cu(In,Ga)Se2 Solar Cells With a Flat Ga profile
  • 2018
  • Ingår i: IEEE Journal of Photovoltaics. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-3381 .- 2156-3403. ; 8:3, s. 864-870
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, Cu(In, Ga)Se2 solar cells with a high bandgap (1.31 eV) and a flat Ga profile ([Ga]/([Ga]+[In]) ≈ 0.60) were examined. For absorber layer thicknesses varying from 0.60 to 1.45 μm, the Mo rear contact of one set of samples was passivated with an ultrathin (27 nm) Al2O3 layer with point contact openings, and compared with reference samples where the rear contact remained unpassivated. For the passivated samples, mainly large gains in the short-circuit current led to an up to 21% (relative) higher power conversion efficiency compared with unpassivated cells. The differences in temperature-dependent current voltage behavior between the passivated and the unpassivated samples and the thin and the thick samples can be explained by an oppositely poled secondary photodiode at the rear contact.
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15.
  • Ledinek, Dorothea, et al. (författare)
  • Rear contact passivation for high bandgap Cu(In,Ga)Se2 solar cells with varying absorber thickness and flat Ga profile
  • 2017
  • Ingår i: 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC). - : IEEE. - 9781509056057 ; , s. 796-801
  • Konferensbidrag (refereegranskat)abstract
    • In this study, six samples of Cu(In,Ga)Se2 solar cells with a high band gap (1.31 eV) and a flat Ga profile ([Ga]I([Ga]+[In]) approximate to 0.60) were produced. For every nominal absorber thickness of 0.5, 1.0 and 1.5 gm, the Mo rear contact of one sample was passivated with a 27 nm thick Al2O3 passivation layer with point contact openings, while the other sample's rear contact remained unpassivated. For the passivated cells, mainly large gains in the short circuit current lead to an up to 21%, 13% and 14% (relative) higher power conversion efficiency compared to the unpassivated cells.
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16.
  • Lindahl, Johan, et al. (författare)
  • Inline Cu(In,Ga)Se-2 Co-evaporation for High-Efficiency Solar Cells and Modules
  • 2013
  • Ingår i: IEEE JOURNAL OF PHOTOVOLTAICS. - 2156-3381. ; 3:3, s. 1100-1105
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, co-evaporation of Cu(In,Ga)Se-2 (CIGS) in an inline single-stage process is used to fabricate solar cell devices with up to 18.6% conversion efficiency using a CdS buffer layer and 18.2% using a Zn1-xSnxOy Cd-free buffer layer. Furthermore, a 15.6-cm(2) mini-module, with 16.8% conversion efficiency, has been made with the same layer structure as the CdS baseline cells, showing that the uniformity is excellent. The cell results have been externally verified. The CIGS process is described in detail, and material characterization methods show that the CIGS layer exhibits a linear grading in the [Ga]/([Ga]+[In]) ratio, with an average [Ga]/([Ga]+[In]) value of 0.45. Standard processes for CdS as well as Cd-free alternative buffer layers are evaluated, and descriptions of the baseline process for the preparation of all other steps in the Angstrom Solar Center standard solar cell are given.
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17.
  • Lontchi, Jackson, et al. (författare)
  • Optimization of Back Contact Grid Size in Al2O3-Rear-Passivated Ultrathin CIGS PV Cells by 2-D Simulations
  • 2020
  • Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 10:6, s. 1908-1917
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a simulation strategy using ATLAS-2D to optimize the back-contact hole grid (i.e., size and pitch of openings) of the Al 2 O 3 -rear-passivation layer in ultrathin Cu(In,Ga)Se 2 photovoltaic cells. We first discuss and compare our simulation model with a series of experimental nonpassivated and passivated cells to decouple the crucial passivation parameters. The simulation results follow the experimental trends, highlighting the beneficial effects of the passivation on the cell performances. Furthermore, it stresses the influence of the passivation quality at the Al 2 O 3 /Cu(In,Ga)Se 2 (CIGS) interface and of the contact resistance at the Mo/CIGS interface within the openings. Further simulations quantify significant improvements in short-circuit current and open-circuit voltage for different sizes of openings in the Al 2 O 3 layer, relative to an excellent passivation quality (i.e., high density of negative charges in the passivation layer). However, a degradation is predicted for a poor passivation (i.e., low density of such charges) or a high contact resistance. Consequently, we point out an optimum in efficiency when varying the opening widths at fixed hole-pitch and fixed contact resistance. At equivalent contact resistance, simulations predict that the sizes of the pitch and openings can be increased without optimal performance losses when maintaining a width to pitch ratio around 0.2. This simulation trends have been confirmed by a series of experiments, indicating that it is crucial to care about the dimensions of the opening grid and the contact resistance of passivated cells. These simulation results provide significant insights for optimal cell design and characterizations of passivated UT-CIGS PV cells.
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18.
  • Lontchi, Jackson, et al. (författare)
  • Ultra-thin CIGS : 2D Modelling and impactful results for optimal cell design and characterizations
  • 2020
  • Ingår i: 2020 47th IEEE Photovoltaic Specialists Conference (PVSC). - 9781728161150 - 9781728161167 ; , s. 699-700
  • Konferensbidrag (refereegranskat)abstract
    • We present a 2D model of an Al 2 O 3 -passivated ultrathin Cu(In, Ga)Se 2 photovoltaic cell with rear-contact pattern. Simulation results follow the experimental trends, highlighting the significant effects of the passivation quality and of the Mo/CIGS contact resistance. Improvements in Jsc and Voc are discussed for different sizes of openings, relative to an excellent passivation quality (i.e. high density of negative charges in the passivation layer). However, a degradation is predicted for a poor passivation (i.e. low density of such charges) or a high contact resistance. We point out an optimum in efficiency when varying the opening widths at fixed hole-pitch and fixed contact resistance for a width to pitch ratio around 0.2. These simulation results provide significant insights for optimal cell design and characterizations of passivated UT-CIGS PV cells.
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19.
  • Lopes, Tomas S., et al. (författare)
  • Rear Optical Reflection and Passivation Using a Nanopatterned Metal/Dielectric Structure in Thin-Film Solar Cells
  • 2019
  • Ingår i: IEEE Journal of Photovoltaics. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2156-3381 .- 2156-3403. ; 9:5, s. 1421-1427
  • Tidskriftsartikel (refereegranskat)abstract
    • Currently, one of the main limitations in ultrathin Cu(In,Ga)Se-2 (CIGS) solar cells are the optical losses, since the absorber layer is thinner than the light optical path. Hence, light management, including rear optical reflection, and light trapping is needed. In this paper, we focus on increasing the rear optical reflection. For this, a novel structure based on having a metal interlayer in between the Mo rear contact and the rear passivation layer is presented. In total, eight different metallic interlayers are compared. For the whole series, the passivation layer is aluminum oxide (Al2O3). The interlayers are used to enhance the reflectivity of the rear contact and thereby increasing the amount of light reflected back into the absorber. In order to understand the effects of the interlayer in the solar cell performance both from optical and/or electrical point of view, optical simulations were performed together with fabrication and electrical measurements. Optical simulations results are compared with current density-voltage (J-V) behavior and external quantum efficiency measurements. A detailed comparison between all the interlayers is done, in order to identify the material with the greatest potential to he used as a rear reflective layer for ultrathin CIGS solar cells and to establish fabrication challenges. The Ti-W alloy is a promising a rear reflective layer since it provides solar cells with light to power conversion efficiency values of 9.9%, which is 2.2% (abs) higher than the passivated ultrathin sample and 3.7% (abs) higher than the unpassivated ultrathin reference sample.
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20.
  • Monteiro, Margarida, et al. (författare)
  • X-ray Photoelectron Spectroscopy for Studying Passivation Architectures of Cu(In,Ga)Se-2 Cells
  • 2021
  • Ingår i: 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665419222 ; , s. 890-892
  • Konferensbidrag (refereegranskat)abstract
    • Optoelectronic devices are susceptible to interface recombination, which can have a detrimental impact on their performance. Therefore, there is an urgent need for tailored passivation strategies to reach a technological boost. In this contribution, two architectures based on passivated Cu(In, Ga)Se-2 solar cells are analyzed with X-ray photoelectron spectroscopy (XPS): one based on rear passivation with gold nanoparticle aggregates, and the other with Al2O3 as a front passivation layer. It is demonstrated that XPS can assist in the understanding of passivated devices from a chemical point of view, comprehend their limitations and push forward the development of future devices.
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21.
  • Oliveira, Antonio, et al. (författare)
  • Over 100 mV VOC Improvement for Rear Passivated ACIGS Ultra-Thin Solar Cells
  • 2023
  • Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlagsgesellschaft. - 1616-301X .- 1616-3028. ; 33:44
  • Tidskriftsartikel (refereegranskat)abstract
    • A decentralized energy system requires photovoltaic solutions to meet new aesthetic paradigms, such as lightness, flexibility, and new form factors. Notwithstanding, the materials shortage in the Green Transition is a concern gaining momentum due to their foreseen continuous demand. A fruitful strategy to shrink the absorber thickness, meeting aesthetic and shortage materials consumption targets, arises from interface passivation. However, a deep understanding of passivated systems is required to close the efficiency gap between ultra-thin and thin film devices, and to mono-Si. Herein, a (Ag,Cu)(In,Ga)Se-2 ultra-thin solar cell, with 92% passivated rear interface area, is compared with a conventional nonpassivated counterpart. A thin MoSe2 layer, for a quasi-ohmic contact, is present in the two architectures at the contacts, despite the passivated device narrow line scheme. The devices present striking differences in charge carrier dynamics. Electrical and optoelectronic analysis combined with SCAPS modelling suggest a lower recombination rate for the passivated device, through a reduction on the rear surface recombination velocity and overall defects, comparing with the reference solar cell. The new architecture allows for a 2% efficiency improvement on a 640 nm ultra-thin device, from 11% to 13%, stemming from an open circuit voltage increase of 108 mV.
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22.
  • Oliveira, Kevin, et al. (författare)
  • SiO$_x$ Patterned Based Substrates Implemented in Cu(In,Ga)Se$_2$ Ultrathin Solar Cells : Optimum Thickness
  • 2022
  • Ingår i: IEEE Journal of Photovoltaics. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-3381 .- 2156-3403. ; 12:4, s. 954-961
  • Tidskriftsartikel (refereegranskat)abstract
    • Interface recombination in sub-mu m optoelectronics has a major detrimental impact on devices' performance, showing the need for tailored passivation strategies to reach a technological boost. In this article, SiO$_x$ passivation based substrates were developed and integrated into ultrathin Cu(In,Ga)Se$_2$ (CIGS) solar cells. This article aims to understand the impact of a passivation strategy, which uses several SiO$_x$ layer thicknesses (3, 8, and 25 nm) integrated into high-performance substrates (HPS). The experimental study is complemented with 3-D lumerical finite-difference time-domain and 2-D Silvaco ATLAS optical and electrical simulations, respectively, to perform a decoupling of optical and electronic gains, allowing for a deep discussion on the impact of the SiO$_x$ layer thickness in the CIGS solar cell performance. This article shows that as the passivation layer thickness increases, a rise in parasitic losses is observed. Hence, a balance between beneficial passivation and optical effects with harmful architectural constraints defines a threshold thickness to attain the best solar cell performance. Analyzing their electrical parameters, the 8-nm novel SiO$_x$ based substrate achieved a light to power conversion efficiency value of 13.2%, a 1.3% absolute improvement over the conventional Mo substrate (without SiO$_x$).
  •  
23.
  • Oliveira, Kevin, et al. (författare)
  • SiOx patterned based substrates implemented in Cu(In,Ga)Se-2 ultrathin solar cells : optimum thickness
  • 2021
  • Ingår i: 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665419222 ; , s. 928-930
  • Konferensbidrag (refereegranskat)abstract
    • Interface recombination in sub-mu m optoelectronic devices has a major harmful impact in devices performance, showing the need for tailored passivation strategies in order to reach a technological boost. In this work, SiOx based substrates were developed and integrated in ultrathin CIGS solar cells. This study aims at understanding the impact of several SiOx layer thicknesses (3, 8 and 25 nm) when this material is used as a passivation layer. Analysing their electrical parameters, the 8 nm novel SiOx based substrates achieved light to power conversion efficiency values up to 13.2 %, a 1.3 % absolute improvement over the conventional substrate (without SiOx).
  •  
24.
  • Salome, Pedro M. P., et al. (författare)
  • A comparison between thin film solar cells made from co-evaporated CuIn1-xGaxSe2 using a one-stage process versus a three-stage process
  • 2015
  • Ingår i: Progress in Photovoltaics. - : Wiley. - 1062-7995 .- 1099-159X. ; 23:4, s. 470-478
  • Tidskriftsartikel (refereegranskat)abstract
    • Until this day, the most efficient Cu(In,Ga)Se-2 thin film solar cells have been prepared using a rather complex growth process often referred to as three-stage or multistage. This family of processes is mainly characterized by a first step deposited with only In, Ga and Se flux to form a first layer. Cu is added in a second step until the film becomes slightly Cu-rich, where-after the film is converted to its final Cu-poor composition by a third stage, again with no or very little addition of Cu. In this paper, a comparison between solar cells prepared with the three-stage process and a one-stage/in-line process with the same composition, thickness, and solar cell stack is made. The one-stage process is easier to be used in an industrial scale and do not have Cu-rich transitions. The samples were analyzed using glow discharge optical emission spectroscopy, scanning electron microscopy, X-ray diffraction, current-voltage-temperature, capacitance-voltage, external quantum efficiency, transmission/reflection, and photoluminescence. It was concluded that in spite of differences in the texturing, morphology and Ga gradient, the electrical performance of the two types of samples is quite similar as demonstrated by the similar J-V behavior, quantum spectral response, and the estimated recombination losses. 
  •  
25.
  • Salome, Pedro M. P., et al. (författare)
  • Cd and Cu Interdiffusion in Cu(In, Ga) Se-2/CdS Hetero-Interfaces
  • 2017
  • Ingår i: IEEE Journal of Photovoltaics. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-3381 .- 2156-3403. ; 7:3, s. 858-863
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a detailed characterization of an industrylike prepared Cu(In, Ga) Se-2 (CIGS)/CdS heterojunction by scanning transmission electron microscopy and photoluminescence (PL). Energy dispersive X-ray spectroscopy shows the presence of several regions in the CIGS layer that are Cu deprived and Cd enriched, suggesting the segregation of Cd-Se. Concurrently, the CdS layer shows Cd-deprived regions with the presence of Cu, suggesting a segregation of Cu-S. The two types of segregations are always found together, which, to the best of our knowledge, is observed for the first time. The results indicate that there is a diffusion process that replaces Cu with Cd in the CIGS layer and Cd with Cu in the CdS layer. Using a combinatorial approach, we identified that this effect is independent of focused-ion beam sample preparation and of the transmission electron microscopy grid. Furthermore, PL measurements before and after an HCl etch indicate a lower degree of defects in the postetch sample, compatible with the segregates removal. We hypothesize that Cu2-x Se nanodomains react during the chemical bath process to form these segregates since the chemical reaction that dominates this process is thermodynamically favorable. These results provide important additional information about the formation of the CIGS/CdS interface.
  •  
26.
  • Salomé, Pedro M. P., et al. (författare)
  • Cu(In,Ga)Se-2 Solar Cells With Varying Na Content Prepared on Nominally Alkali-Free Glass Substrates
  • 2013
  • Ingår i: IEEE Journal of Photovoltaics. - 2156-3381. ; 3:2, s. 852-858
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, Cu(In,Ga)Se-2 (CIGS) thin-film solar cells are prepared on nominally alkali-free glass substrates using an in-line CIGS growth process. As compared with, for example, borosilicate glass or quartz, the glass is engineered to have similar thermal expansion coefficient as soda-lime glass (SLG) but with alkali content close to zero. Na is incorporated in the CIGS material using an ex-situ deposited NaF precursor layer evaporated onto the Mo back contact. Several thicknesses of the NaF layer were tested. The results show that there is a process window, between 15 and 22.5 nm NaF, where the solar cell conversion efficiency is comparable with or exceeding that of SLG references. The effect of an NaF layer that is too thin on the solar cell parameters was mainly lowering the open-circuit voltage, which points to a lower effective dopant concentration in the CIGS layer and is also consistent with presented C-V measurements and modeling results. For excessively thick NaF layers, delamination of the CIGS layer occurred. Additional measurements, such as scanning electron microscopy (SEM), secondary ion mass spectrometry, capacitance-voltage analysis (C-V), time-resolved photoluminescence (TRPL), external quantum efficiency (EQE), current-voltage analysis (J-V), and modeling, are presented, and the results are discussed.
  •  
27.
  • Salome, Pedro M. P., et al. (författare)
  • Incorporation of Na in Cu(In,Ga)Se-2 Thin-Film Solar Cells : A Statistical Comparison Between Na From Soda-Lime Glass and From a Precursor Layer of NaF
  • 2014
  • Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 4:6, s. 1659-1664
  • Tidskriftsartikel (refereegranskat)abstract
    • The presence of Na in Cu(In,Ga)Se-2 layers increases the electrical performance of this type of thin- film solar cell. A detailed comparison of incorporating Na in the CIGS layer by two different methods is performed by evaluating several hundred devices fabricated under similar conditions. The firstmethod is based on the conventionally used Na diffusion from the soda-lime glass substrate, whereas the second method is based on a NaF precursor layer deposited on a Mo- coated alkali- free glass substrate. The sample where Na is introduced by using a NaF precursor layer shows an orientation weighted toward (2 0 4)/(2 2 0) and a net acceptor concentration of 3.4 x 10(16) cm(-3), while SLG shows a (1 1 2) orientation with a 2.9 x 10(16) cm(-3) acceptor concentration. Both sample types show close identical elemental depth profiles, morphology, and electrical performance.
  •  
28.
  • Salome, Pedro M. P., et al. (författare)
  • Influence of CdS and ZnSnO Buffer Layers on the Photoluminescence of Cu(In,Ga)Se-2 Thin Films
  • 2017
  • Ingår i: IEEE Journal of Photovoltaics. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-3381 .- 2156-3403. ; 7:2, s. 670-675
  • Tidskriftsartikel (refereegranskat)abstract
    • The search for alternatives to the CdS buffer layer in Cu(In,Ga)Se-2 (CIGS) solar cells has turned out to be quite promising in terms of power conversion efficiency. In this paper, the typically used chemical-bath-deposited CdS layer is compared with an atomic-layer-deposited Zn1-xSnxOy (ZnSnO). An optical study by external quantum efficiency and photoluminescence on the influence of different buffer layers on the defect properties of CIGS is presented. For both buffer layers, the CIGS bulk and CIGS/buffer interface are strongly influenced by electrostatic fluctuating potentials, which are less pronounced for the sample with the ZnSnO buffer layer. This is associated with a lower concentration of donor defects at the CIGS near-interface layer. A change in the bandgap of the CIGS as a consequence of the buffer layer deposition is observed. This study expands the knowledge of defects in the complex quaternary semiconductor CIGS, which, as discussed, can be affected even by the choice of buffer layer and its deposition process.
  •  
29.
  • Salome, Pedro M. P., et al. (författare)
  • Passivation of Interfaces in Thin Film Solar Cells : Understanding the Effects of a Nanostructured Rear Point Contact Layer
  • 2018
  • Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 5:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Thin film solar cells based in Cu(In,Ga)Se-2 (CIGS) are among the most efficient polycrystalline solar cells, surpassing CdTe and even polycrystalline silicon solar cells. For further developments, the CIGS technology has to start incorporating different solar cell architectures and strategies that allow for very low interface recombination. In this work, ultrathin 350 nm CIGS solar cells with a rear interface passivation strategy are studied and characterized. The rear passivation is achieved using an Al2O3 nanopatterned point structure. Using the cell results, photoluminescence measurements, and detailed optical simulations based on the experimental results, it is shown that by including the nanopatterned point contact structure, the interface defect concentration lowers, which ultimately leads to an increase of solar cell electrical performance mostly by increase of the open circuit voltage. Gains to the short circuit current are distributed between an increased rear optical reflection and also due to electrical effects. The approach of mixing several techniques allows us to make a discussion considering the different passivation gains, which has not been done in detail in previous works. A solar cell with a nanopatterned rear contact and a 350 nm thick CIGS absorber provides an average power conversion efficiency close to 10%.
  •  
30.
  • Salomé, Pedro M. P., et al. (författare)
  • Secondary crystalline phases identification in CuZnSnSe thin films : contributions from Raman scattering and photoluminescence
  • 2014
  • Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 49:21, s. 7425-7436
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, we present the Raman peak positions of the quaternary pure selenide compound CuZnSnSe (CZTSe) and related secondary phases that were grown and studied under the same conditions. A vast discussion about the position of the X-ray diffraction (XRD) reflections of these compounds is presented. It is known that by using XRD only, CZTSe can be identified but nothing can be said about the presence of some secondary phases. Thin films of CZTSe, CuSnSe, ZnSe, SnSe, SnSe, MoSe and a-Se were grown, which allowed their investigation by Raman spectroscopy (RS). Here we present all the Raman spectra of these phases and discuss the similarities with the spectra of CZTSe. The effective analysis depth for the common back-scattering geometry commonly used in RS measurements, as well as the laser penetration depth for photoluminescence (PL) were estimated for different wavelength values. The observed asymmetric PL band on a CZTSe film is compatible with the presence of CZTSe single-phase and is discussed in the scope of the fluctuating potentials' model. The estimated bandgap energy is close to the values obtained from absorption measurements. In general, the phase identification of CZTSe benefits from the contributions of RS and PL along with the XRD discussion.
  •  
31.
  • Salome, Pedro M. P., et al. (författare)
  • The effect of high growth temperature on Cu(In,Ga)Se-2 thin film solar cells
  • 2014
  • Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 123, s. 166-170
  • Tidskriftsartikel (refereegranskat)abstract
    • The morphological, elemental distribution and electrical performance effects of increasing the Cu(In,Ga) Se-2 (CIGS) growth substrate temperature are studied. While the increased substrate growth temperature with no other modifications led to increased CIGS grain size, it also resulted in depth profile flattening of the [Ga]/([Ga]+[In]) ratio. Tuning the Ga profile in the high temperature process led to a more desirable [Ga]/([Ga]+[In]) depth profile and allowed a comparison between high and standard temperature. Devices prepared at higher temperature showed an improved grain size and the electrical performance is very similar to that of the reference sample prepared at a standard temperature.
  •  
32.
  • Salomé, Pedro M. P., et al. (författare)
  • The effect of Mo back contact ageing on Cu(In,Ga)Se-2 thin-film solar cells
  • 2014
  • Ingår i: Progress in Photovoltaics. - : Wiley. - 1062-7995 .- 1099-159X. ; 22:1, s. 83-89
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, we investigate the effect of ageing Mo-coated substrates in a dry and N-2 flooded cabinet. The influence was studied by preparing Cu(In,Ga)Se-2 solar cells and by comparing the electrical performance with devices where the Mo layer was not aged. The measurements used for this study were current-voltage (J-V), external quantum efficiency (EQE), secondary ion mass spectroscopy (SIMS) and capacitance-voltage (C-V). It was concluded that devices prepared with the aged Mo layer have, in average, an increase of 0.8% in efficiency compared with devices that had a fresh Mo layer. Devices with aged Mo exhibited a nominal increase of 12.5mV of open circuit voltage, a decrease of 1.1mA/cm(-2) of short circuit current and a fill factor increase of 2.4%. Heat treatment of fresh Mo layers in oxygen atmosphere was also studied as an alternative to ageing and was shown to provide a similar effect to the aged device's performance. 
  •  
33.
  • Salomé, Pedro, et al. (författare)
  • Na doping of CIGS solar cells using low sodium-doped mo layer
  • 2013
  • Ingår i: IEEE Journal of Photovoltaics. - 2156-3381. ; 3:1, s. 509-513
  • Tidskriftsartikel (refereegranskat)abstract
    • Na plays an important role in the electrical performance of Cu(In,Ga)Se2 (CIGS) thin-film solar cells. Traditionally, Na has been introduced during the growth of CIGS by thermal diffusion from the soda-lime glass (SLG) substrate; however, better control of the amount of Na is needed to have a more precise control of growth conditions. The introduction of Na into CIGS was studied in three different ways: from the SLG, from a NaF precursor, and from a Na-doped Mo (MoNa) back contact. The most successful approaches were obtained by using the conventional SLG and the NaF precursor. Different growth temperatures of CIGS were tested in an attempt to diffuse more Na from the MoNa layer.
  •  
34.
  • Sousa, M. G., et al. (författare)
  • Cu2ZnSnS4 absorber layers obtained through sulphurization of metallic precursors : Graphite box versus sulphur flux
  • 2013
  • Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 535, s. 27-30
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work we employed a hybrid method, combining RF-magnetron sputtering with evaporation, for the deposition of tailor made metallic precursors, with varying number of Zn/Sn/Cu (ZTC) periods and compared two approaches to sulphurization. Two series of samples with 1x, 2x and 4x ZTC periods have been prepared. One series of precursors was sulphurized in a tubular furnace directly exposed to a sulphur vapour and N-2 + 5% H-2 flux at a pressure of 5.0 x 10(+4) Pa. A second series of identical precursors was sulphurized in the same furnace but inside a graphite box where sulphur pellets have been evaporated again in the presence of N-2 + 5% H-2 and at the same pressure as for the sulphur flux experiments. The morphological and chemical analyses revealed a small grain structure but good average composition for all three films sulphurized in the graphite box. As for the three films sulphurized in sulphur flux grain growth was seen with the increase of the number of ZTC periods whilst, in terms of composition, they were slightly Zn poor. The films' crystal structure showed that Cu2ZnSnS4 is the dominant phase. However, in the case of the sulphur flux films SnS2 was also detected. Photoluminescence spectroscopy studies showed an asymmetric broad band emission which occurs in the range of 1-1.5 eV. Clearly the radiative recombination efficiency is higher in the series of samples sulphurized in sulphur flux. We have found that sulphurization in sulphur flux leads to better film morphology than when the process is carried out in a graphite box in similar thermodynamic conditions. Solar cells have been prepared and characterized showing a correlation between improved film morphology and cell performance. The best cells achieved an efficiency of 2.4%.
  •  
35.
  • Szaniawski, Piotr, et al. (författare)
  • Influence of Varying Cu Content on Growth and Performance of Ga-Graded Cu(In,Ga)Se-2 Solar Cells
  • 2015
  • Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 5:6, s. 1775-1782
  • Tidskriftsartikel (refereegranskat)abstract
    • Cu(In,Ga)Se-2 thin-film solar cells with Ga-graded absorber layers and a [Cu]/([In] + [Ga]) ratio varying between 0.5 and 1.0 were prepared by coevaporation and investigated. Except for the sample with a final [Cu]/([In] + [Ga]) ratio of 1.0, the samples were Cu-poor at all times during the evaporation. The variation in copper was found to influence the material properties in several ways: 1) Changing the Cu content had a strong impact on In and Ga interdiffusion, resulting in decreased Ga gradients in samples with large Cu deficiency; 2) the Cu-poor Cu(In, Ga)(3)Se-5 phase was detected in absorbers with [Cu]/([In] + [Ga]) ratios of 0.65 and below; and 3) the grain size changed significantly with the Cu variation. We observe a trend of reduced solar cell efficiencies for [Cu]/([In] + [Ga]) ratios of 0.65 and below, with an efficiency of 13.4% for the sample with a [Cu]/([In] + [Ga]) ratio of only 0.5, i.e., far from stoichiometry. We tentatively attribute the efficiency loss to a high concentration of point defects caused by the Cu deficiency.
  •  
36.
  • Teixeira, Jennifer P., et al. (författare)
  • Recombination Channels in Cu(In,Ga)Se2 Thin Films : Impact of the Ga-Profile
  • 2020
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:23, s. 12295-12304
  • Tidskriftsartikel (refereegranskat)abstract
    • Depth bandgap profiles via a [Ga]/([Ga]+[In]) variation in the Cu(In,Ga)Se-2 (CIGS) absorber layer have been implemented as a strategy to enhance the performance of CIGS solar cells. Since the [Ga]/([Ga]+[In]) determines to a large extent the position of the conduction band minimum, different Ga-profiles lead to different electronic energy levels structures throughout the CIGS layer. In this paper, from the investigation of the dependence of the photoluminescence (PL) on excitation power and temperature, we critically analyze the impact of a notch or a linear Ga-profile on the CIGS electronic energy levels structure and subsequent dominant recombination channels. Notwithstanding, two radiative transitions involving fluctuating potentials were observed for each sample, and significant differences in the luminescence resulting from the two Ga-profiles were identified. For the CIGS absorber with a notch Ga-profile, two tail-impurity radiative transitions involving equivalent donor clusters and the same deep acceptor level were ascribed to the CIGS/CdS interface region and to the notch region. The probability of radiative recombination in these two regions is discussed. For the CIGS absorber with a linear Ga-profile, two band-impurity radiative transitions involving an acceptor, with an ionization energy compatible with the V-Cu defect were ascribed to the CIGS/CdS interface region. Our results show that the dominant acceptor defects are dependent on the Ga-profile, and they also highlight the complexity of the radiative and nonradiative recombination channels revealed by the tight control of the parameters in the experiment.
  •  
37.
  • Vermang, Bart, 1981-, et al. (författare)
  • Development of Rear Surface Passivated Cu(In,Ga)Se2 Thin Film Solar Cells with Nano-Sized Local Rear Point Contacts
  • 2013
  • Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 117:SI, s. 505-511
  • Tidskriftsartikel (refereegranskat)abstract
    • For the first time, a novel rear contacting structure for copper indium gallium (di)selenide (CIGS) thin film solar cells is discussed theoretically, developed in an industrially viable way, and demonstrated in tangible devices. The proposed cell design reduces back contacting area by combining a rear surface passivation layer and nano-sized local point contacts. Atomic layer deposition (ALD) of Al2O3 is used to passivate the CIGS surface and the formation of nano-sphere shaped precipitates in chemical bath deposition (CBD) of CdS to generate point contact openings. The Al2O3 rear surface passivated CIGS solar cells with nano-sized local rear point contacts show a significant improvement in open circuit voltage (VOC) compared to unpassivated reference cells. Comparing the passivated devices to solar cell capacitance simulator (SCAPS) modeling indicates that this increase is attributed to a decrease in rear surface recombination of a few orders.
  •  
38.
  • Vermang, Bart, et al. (författare)
  • Introduction of Si PERC Rear Contacting Designto Boost Efficiency of Cu(In,Ga)Se2 Solar Cells
  • 2014
  • Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 4:6, s. 1644-1649
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently, Cu(In,Ga)Se-2 (CIGS) solar cells have achieved 21% world-record efficiency, partly due to the introduction of a postdeposition potassium treatment to improve the front interface of CIGS absorber layers. However, as high-efficiency CIGS solar cells essentially require long diffusion lengths, the highly recombinative rear of these devices also deserves attention. In this paper, an Al2O3 rear surface passivation layer with nanosized local point contacts is studied to reduce recombination at the standard Mo/CIGS rear interface. First, passivation layers with well-controlled grids of nanosized point openings are established by use of electron beam lithography. Next, rear-passivated CIGS solar cells with 240-nm-thick absorber layers are fabricated as study devices. These cells show an increase in open-circuit voltage (+57 mV), short-circuit current (+3.8 mA/cm(2)), and fill factor [9.5% (abs.)], compared with corresponding unpassivated reference cells, mainly due to improvements in rear surface passivation and rear internal reflection. Finally, solar cell capacitance simulator (SCAPS) modeling is used to calculate the effect of reduced back contact recombination on high-efficiency solar cells with standard absorber layer thickness. The modeling shows that up to 50-mV increase in open-circuit voltage is anticipated.
  •  
39.
  • Vermang, Bart, et al. (författare)
  • Rear surface optimization of CZTS solar cells by use of a passivation layer with nano-sized point openings
  • 2015
  • Ingår i: 2015 IEEE 42ND PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC). - 9781479979448
  • Konferensbidrag (refereegranskat)abstract
    • Previously, an innovative way to reduce rear interface recombination of Cu(In,Ga)(S,Se)(2) (CIGSSe) solar cells has been successfully developed. In this work, this concept is established in Cu-2(Zn,Sn)(S,Se)(4) (CZTSSe) cells, to demonstrate its potential for other thin-film technologies. Therefore, ultra-thin CZTS cells with an Al2O3 rear surface passivation layer having nano-sized point openings are fabricated. The results indicate that introducing such a passivation layer can have a positive impact on open circuit voltage (V-OC; +49%(rel.)) or short circuit current (J(SC); +17%(rel.)), compared to corresponding unpassivated cells. Hence, a promising efficiency improvement of 52%(rel.) is obtained for the rear passivated cells.
  •  
40.
  • Vermang, Bart, et al. (författare)
  • Rear Surface Optimization of CZTS Solar Cells by Use of a Passivation Layer With Nanosized Point Openings
  • 2016
  • Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 6:1, s. 332-336
  • Tidskriftsartikel (refereegranskat)abstract
    • Previously, an innovative way to reduce rear interface recombination in Cu(In, Ga)(S, Se)(2) (CIGSSe) solar cells has been successfully developed. In this work, this concept is established in Cu-2(Zn, Sn)(S, Se)(4) (CZTSSe) cells to demonstrate its potential for other thin-film technologies. Therefore, ultrathin CZTS cells with an Al2O3 rear surface passivation layer having nanosized point openings are fabricated. The results indicate that introducing such a passivation layer can have a positive impact on open-circuit voltage (V-OC; +17% rel.), short-circuit current (J(SC); +5% rel.), and fill factor (FF; +9% rel.), compared with corresponding unpassivated cells. Hence, a promising efficiency improvement of 32% rel. is obtained for the rear passivated cells.
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41.
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