| 1. |
- Andersson, Olof, et al.
(författare)
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Enhancing Open-Circuit Voltage in Gradient Organic Solar Cells by Rectifying Thermalization Losses
- 2020
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Ingår i: Solar RRL. - : Wiley-VCH Verlagsgesellschaft. - 2367-198X. ; 4:12
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Tidskriftsartikel (refereegranskat)abstract
- In virtually all solar cells, including optimized ones that operate close to the Shockley-Queisser (SQ) limit, thermalization losses are a major, efficiency-limiting factor. In typical bulk heterojunction organic solar cells, the loss of the excess energy of photocreated charge carriers in the disorder-broadened density of states is a relatively slow process that for commonly encountered disorder values takes longer than the charge extraction time. Herein, it is demonstrated by numerical modeling that this slow relaxation can be rectified by means of a linear gradient in the donor:acceptor ratio between anode and cathode. For experimentally relevant parameters, open-circuit voltage (VOC) enhancements up to approximate to 0.2 V in combination with significant enhancements in fill factor as compared to devices without gradient are found. The VOC enhancement can be understood in terms of a simple nonequilibrium effective temperature model. Implications for existing and future organic photovoltaics (OPV) devices are discussed.
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| 2. |
- Aung, Soe Ko Ko, et al.
(författare)
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Improved Efficiency of Perovskite Solar Cells with Low-Temperature-Processed Carbon by Introduction of a Doping-Free Polymeric Hole Conductor
- 2022
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 6:8
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Tidskriftsartikel (refereegranskat)abstract
- Low-temperature-processed carbon-based perovskite solar cells (C-PSCs) are promising photovoltaic devices, because of their good stability, low cost, and simple preparation methods, which allow for scalable processing. Herein, C-PSCs with the n-i-p structure are prepared, using a SnO2 nanoparticles film as the electron-selective contact, MAPbI(3) perovskite as the intrinsic absorber layer (MA = methylammonium), and a carbon layer as the hole-selective layer and conductor. Carbon is, however, not an ideal hole-selective layer and it is found that improved solar cell performance can be obtained by introducing a polymeric hole conductor between the perovskite and the carbon layer. Specifically, undoped poly(3-hexylthiophene) (P3HT) is used for this purpose, as it is stable and highly hydrophobic. For ITO/SnO2/MAPbI(3)/carbon devices, a solar cell efficiency of up to 12.8% is obtained, increasing up to 15.7% with the inclusion of a P3HT layer, which increases open-circuit potential, photocurrent, and fill factor (FF). In comparison, ITO/SnO2/MAPbI(3)/P3HT/Au devices performed rather poorly (up to 11.7%). Encouraging stability is obtained for unencapsulated C-PSC devices: P3HT/carbon devices do not show any degradation in solar cell performance upon storage for 1 month in low humidity, while they maintain 70% of their initial efficiency after 900 h at 82 degrees C in air.
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| 3. |
- Bogachuk, Dmitry, et al.
(författare)
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Rethinking Electrochemical Deposition of Nickel Oxide for Photovoltaic Applications
- 2024
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- A thin layer of sputtered or wet-processed nickel oxide (NiOx) is often used to fabricate perovskite solar cells (PSCs). Remarkably, NiOx can also be deposited by a recently developed electrochemical method, which is considered promising due to its short processing time, absence of high-vacuum conditions, and ease of manufacturing. Such electrochemically deposited NiOx (eleNiOx) is obtained by applying an electric bias to the front electrode of a PSC or perovskite solar module (PSM). Therefore, the electrode sheet resistance affects the current distribution through it, creating a gradient in the amount of charge provided for the electrochemical reaction. Consequently, this leads to the inhomogeneity in the formed eleNiOx, which has numerous implications on the final photovoltaic performance of PSMs. In this work, the interdependencies between the electrode sheet resistance, current distribution, eleNiOx thickness gradient, and the caused power losses of large area PSMs are discussed. By coupling the experimental findings with our numerical simulations, it is found that heterogeneity in surface potential of even small-sized modules can lead to severe differences in local eleNiOx thickness and photovoltaic performance. Therefore the potential drop across the front electrode is an inherent problem of this deposition method and potential approaches are proposed to minimize it. The synergy between several numerical simulation methods and the experimental work provides an additional critical insight into the electrochemical deposition process of nickel oxide and how important it is for the performance and stability of the large-area perovskite photovoltaic modules. It is believed that the conclusions drawn from this study are universally applicable to other electrochemically deposited layers as well.image (c) 2023 WILEY-VCH GmbH
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| 4. |
- Bose, Sourav, et al.
(författare)
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Optical Lithography Patterning of SiO2 Layers for Interface Passivation of Thin Film Solar Cells
- 2018
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Ingår i: Solar RRL. - : Wiley. - 2367-198X. ; 2:12
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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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| 5. |
- Calnan, Sonya, et al.
(författare)
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Development of Various Photovoltaic‐Driven Water Electrolysis Technologies for Green Solar Hydrogen Generation
- 2021
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 6:5
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Tidskriftsartikel (refereegranskat)abstract
- Direct solar hydrogen generation via a combination of photovoltaics (PV) and water electrolysis can potentially ensure a sustainable energy supply while minimizing greenhouse emissions. The PECSYS project aims at demonstrating asolar-driven electrochemical hydrogen generation system with an area >10 m2 with high efficiency and at reasonable cost. Thermally integrated PV electrolyzers(ECs) using thin-film silicon, undoped, and silver-doped Cu(In,Ga)Se2 and silicon heterojunction PV combined with alkaline electrolysis to form one unit are developed on a prototype level with solar collection areas in the range from 64 to2600 cm2 with the solar-to-hydrogen (StH) efficiency ranging from 4 to 13%. Electrical direct coupling of PV modules to a proton exchange membrane EC test the effects of bifacially (730 cm2 solar collection area) and to study the long-term operation under outdoor conditions (10 m2 collection area) is also investigated. In both cases, StH efficiencies exceeding 10% can be maintained over the test periods used. All the StH efficiencies reported are based on measured gas outflow using mass flow meters.
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| 6. |
- Campanari, Valerio, et al.
(författare)
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Reevaluation of Photoluminescence Intensity as an Indicator of Efficiency in Perovskite Solar Cells
- 2022
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 6:8
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Tidskriftsartikel (refereegranskat)abstract
- The photoluminescence (PL) intensity is often used as an indicator of the performance of perovskite solar cells and indeed the PL technique is often used for the characterization of these devices and their constituent materials. Herein, a systematic approach is presented to the comparison of the conversion efficiency and the PL intensity of a cell in both open-circuit (OC) and short-circuit (SC) conditions and its application to multiple heterogeneous devices. It is shown that the quenching of the PL observed in SC conditions is a good parameter to assess the device efficiency. The authors explain the dependence of the PL quenching ratio between OC and SC on the cell efficiency with a simple model that is also able to estimate the carrier extraction time of a device.
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| 7. |
- Cheng, Ming, et al.
(författare)
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A Perylenediimide Tetramer-Based 3D Electron Transport Material for Efficient Planar Perovskite Solar Cell
- 2017
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 1:5
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Tidskriftsartikel (refereegranskat)abstract
- A perylenediimide (PDI) tetramer-based three dimensional (3D) molecular material, termed SFX-PDI4, has been designed, synthesized, and characterized. The low-lying HOMO and LUMO energy levels, high electron mobility and good film-formation property make it a promising electron transport material (ETM) in inverted planar perovskite solar cells (PSCs). The device exhibits a high power conversion efficiency (PCE) of 15.3% with negligible hysteresis, which can rival that of device based on PC61BM. These results demonstrate that three dimensional PDI-based molecular materials could serve as high performance ETMs in PSCs.
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| 8. |
- Cunha, Jose M. V., et al.
(författare)
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High-Performance and Industrially Viable Nanostructured SiOx Layers for Interface Passivation in Thin Film Solar Cells
- 2021
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 5:3
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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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| 9. |
- Dagar, Janardan, et al.
(författare)
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Alkali Salts as Interface Modifiers in n-i-p Hybrid Perovskite Solar Cells
- 2019
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Ingår i: Solar RRL. - : Wiley. - 2367-198X. ; 3:9
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Tidskriftsartikel (refereegranskat)abstract
- After demonstration of a 23% power conversion efficiency, a high operational stability is the next most important scientific and technological challenge in perovskite solar cells (PSCs). A potential failure mechanism is tied to a bias-induced ion migration, which causes current–voltage hysteresis and a decay in the device performance over time. Herein, alkali salts are shown to mitigate hysteresis and stabilize device performance in n-i-p hybrid planar PSCs. Different alkali salts of potassium chloride, iodide, and nitrate as well as sodium chloride and iodide are deposited from aqueous solution onto the n-type contact, based on SnO2, prior to deposition of the perovskite absorber Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3. Introduction of potassium-based alkali salts suppresses the current–voltage hysteresis and stabilizes the operational device stability at the maximum power point. This is attributed to the suppression of hole trapping at the n-type selective transport layer (SnO2)/perovskite interface observed by surface photovoltage spectroscopy, which is interpreted to reduce interfacial recombination and improve charge carrier extraction. The best and most stable performance of 19% is achieved using potassium nitrate as the interface modifier. Devices with higher and more stable performance exhibit substantially lower current transients, analyzed during maximum power point tracking.
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| 10. |
- Duan, Chunhui, et al.
(författare)
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Improving Performance of All-Polymer Solar Cells Through Backbone Engineering of Both Donors and Acceptors
- 2018
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Ingår i: Solar RRL. - : Wiley. - 2367-198X. ; 2:12
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Tidskriftsartikel (refereegranskat)abstract
- All-polymer solar cells (APSCs), composed of semiconducting donor and acceptor polymers, have attracted considerable attention due to their unique advantages compared to polymer-fullerene-based devices in terms of enhanced light absorption and morphological stability. To improve the performance of APSCs, the morphology of the active layer must be optimized. By employing a random copolymerization strategy to control the regularity of the backbone of the donor polymers (PTAZ-TPDx) and acceptor polymers (PNDI-Tx) the morphology can be systematically optimized by tuning the polymer packing and crystallinity. To minimize effects of molecular weight, both donor and acceptor polymers have number-average molecular weights in narrow ranges. Experimental and coarse-grained modeling results disclose that systematic backbone engineering greatly affects the polymer crystallinity and ultimately the phase separation and morphology of the all-polymer blends. Decreasing the backbone regularity of either the donor or the acceptor polymer reduces the local crystallinity of the individual phase in blend films, affording reduced short-circuit current densities and fill factors. This two-dimensional crystallinity optimization strategy locates a PCE maximum at highest crystallinity for both donor and acceptor polymers. Overall, this study demonstrates that proper control of both donor and acceptor polymer crystallinity simultaneously is essential to optimize APSC performance.
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