| 1. |
- Goffard, Julie, et al.
(författare)
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Light Trapping in Ultrathin CIGS Solar Cells withNanostructured Back Mirrors
- 2017
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Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 7:5, s. 1433-1441
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Tidskriftsartikel (refereegranskat)abstract
- Novel architectures for light trapping in ultrathinCu(In,Ga)Se2 (CIGS) solar cells are proposed and numericallyinvestigated. They are composed of a flat CIGS layer withnanostructured back mirrors made of highly reflective metals.Multi-resonant absorption is obtained for two different patternsof nanostructured mirrors. It leads to a dramatic increase in theshort-circuit current predicted for solar cells with very thin CIGSlayers. We analyze the resonance phenomena and the density ofphotogenerated carriers in the absorber. We discuss the impactof the material used for the buffer layer (CdS and ZnS) and theback mirror (Mo, Cu, Au, and Ag). We investigate various CIGSthicknesses from 100 to 500 nm, and we compare our numericalresults with experimental data taken from the literature. Wepredict a short-circuit current of Jsc = 33.6 mA/cm2 for a realisticsolar cell made of a 200-nm-thick CIGS absorber with a coppernanostructured mirror. It opens a way toward ultrathin CIGSsolar cells with potential conversion efficiencies up to 20%.
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| 2. |
- Gouillart, Louis, et al.
(författare)
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Interface engineering of ultrathin Cu(In,Ga)Se2 solar cells on reflective back contacts
- 2021
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Ingår i: Progress in Photovoltaics. - : John Wiley & Sons. - 1062-7995 .- 1099-159X. ; 29:2, s. 212-221
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Tidskriftsartikel (refereegranskat)abstract
- Cu(In,Ga)Se-2-based (CIGS) solar cells with ultrathin (<= 500 nm) absorber layers suffer from the low reflectivity of conventional Mo back contacts. Here, we design and investigate ohmic and reflective back contacts (RBC) made of multilayer stacks that are compatible with the direct deposition of CIGS at 500 degrees C and above. Diffusion mechanisms and reactions at each interface and in the CIGS layer are carefully analyzed by energy dispersive X-ray (EDX)/scanning transmission electron microscopy (STEM). It shows that the highly reflective silver mirror is efficiently encapsulated in ZnO:Al layers. The detrimental reaction between CIGS and the top In2O3:Sn (ITO) layer used for ohmic contact can be mitigated by adding a 3 nm thick Al2O3 layer and by decreasing the CIGS coevaporation temperature from 550 degrees C to 500 degrees C. It also improves the compositional grading of Ga toward the CIGS back interface, leading to increased open- circuit voltage and fill factor. The best ultrathin CIGS solar cell on RBC exhibits an efficiency of 13.5% (+1.0% as compared to our Mo reference) with a short-circuit current density of 28.9 mA/cm(2) (+2.6 mA/cm(2)) enabled by double-pass absorption in the 510 nm thick CIGS absorber. RBC are easy to fabricate and could benefit other photovoltaic devices that require highly reflective and conductive contacts subject to high temperature processes.
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| 3. |
- Gouillart, Louis, et al.
(författare)
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Reflective Back Contacts for Ultrathin Cu(In,Ga)Se2-Based Solar Cells
- 2020
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Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 10:1, s. 250-254
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Tidskriftsartikel (refereegranskat)abstract
- We report on the development of highly reflective back contacts (RBCs) made of multilayer stacks for ultrathin CIGS solar cells. Two architectures are compared: they are made of a silver mirror coated either with a single layer of In 2 O 3 :Sn (ITO) or with a bilayer of ZnO:Al/ITO. Due to the improvement of CIGS rear reflectance, both back contacts result in a significant external quantum efficiency enhancement, in agreement with optical simulations. However, solar cells fabricated with Ag/ITO back contacts exhibit a strong shunting behavior. The key role of the ZnO:Al layer to control the morphology of the top ITO layer and to avoid silver diffusion through the back contact is highlighted. For a 500-nm-thick CIGS layer, this optimized RBC leads to a best cell with a short-circuit current of 27.8 mA/cm 2 (+2.2 mA/cm 2 as compared to a Mo back contact) and a 12.2%-efficiency (+2.5% absolute).
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| 4. |
- Lontchi, Jackson, et al.
(författare)
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Optimization of Back Contact Grid Size in Al2O3-Rear-Passivated Ultrathin CIGS PV Cells by 2-D Simulations
- 2020
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Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 10:6, s. 1908-1917
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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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| 5. |
- Lontchi, Jackson, et al.
(författare)
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Ultra-thin CIGS : 2D Modelling and impactful results for optimal cell design and characterizations
- 2020
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Ingår i: 2020 47th IEEE Photovoltaic Specialists Conference (PVSC). - 9781728161150 - 9781728161167 ; , s. 699-700
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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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