CdTe thin-film photovoltaics have demonstrated some of the lowest costs of electricity generation owing to its low material cost and ease of manufacturing. However, the full potential of polycrystalline CdTe photovoltaics can only be realized if the open-circuit voltage can be increased beyond 1 V Open-circuit voltage ~850-900 mV has been consistently observed for state-of-the-art polycrystalline CdTe solar cells. Open-circuit voltage of over 1V has been demonstrated for single crystal CdTe devices by doping with Group V elements. Therefore, this study is aimed at understanding behavior of polycrystalline CdTe devices with arsenic doping, its activation and process and performance optimization in order to overcome current voltage limitations in CdTe solar cells.
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Photovoltaic Characteristics of PERC-Like CdTe Solar Cells
Rapid progress has been achieved in thin film CdTe solar cells, reaching a power conversion efficiency of 22.1 %. Researchers demonstrated a short-circuit current density (Jsc) of ≈ 31 mA/cm2 and a fill factor (FF) of ≈ 79 %, close to the theoretically calculated maximum values. However, the open-circuit voltage (Voc) remains below 0.9 V, much lower than the estimated Voc of 1.2 V. One strategy to improve the Voc is to implement a passivated back-contact on CdTe that can reduce the recombination by repelling minority carriers at the surface (i.e., electrons in CdTe). An aluminum oxide thin film (Al2O3) is an attractive candidate owing to its innate fixed negative charges (1012 ~ 1013 cm-2). Here, we use a patterned Al2O3 layer on CdTe to produce PERC-like CdTe solar cells (CdTe PERC).
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- Award ID(s):
- 2048152
- PAR ID:
- 10505222
- Publisher / Repository:
- Materials Research Society
- Date Published:
- Journal Name:
- Electronic Materials Conference
- Format(s):
- Medium: X
- Location:
- University of California, Santa Barbara
- Sponsoring Org:
- National Science Foundation
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Abstract We fabricate and characterize methylammonium lead halide perovskite film as a novel back contact to CdTe thin‐film solar cells. We apply ~0.75 μm perovskite film at the interface of CdCl2‐activated and Cu‐doped CdTe surface and complete the device with Au back contact. We use Cu/Au back contact as a reference to compare results with novel back contact. Our investigation shows that incorporation of thin layer of perovskite film before the back contact metal reduces back contact barrier effect and improves fill factor (FF) and open‐circuit voltage (VOC) of the solar cells. Our low temperature JV results prove that thin‐film perovskite is a very necessary component in CdTe solar cells to reduce back contact barrier, to minimize interface or surface recombination, to improve collection efficiencies, and to increase the efficiency of solar cells. Our best device shows 7% increase in VOCto 0.875 V and ~7% increase in FF with the highest FF of 81%, and solar cell's efficiency finally increases by 10% with the use of MAPb(I1‐xBrx)3as an interface layer.
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De_Angelis, Filippo (Ed.)An integration of perovskite and cadmium telluride (CdTe) solar cells in a tandem configuration has the potential to yield efficient thin-film tandem solar cells. Owing to the promise of higher efficiency at low cost, the presented study aims to explore the potential for combining this commercially established CdTe photovoltaics (PV) with next-generation perovskite PV. Here, we developed four-terminal (4-T) CdTe/perovskite tandem solar cells, starting with 18.3% efficient near-infrared-transparent perovskite solar cells (NIR-TPSCs) with an average transmission (Tavg) of 24.76% in the 300−900 nm wavelength range. These were then integrated with 19.56% efficient opaque CdTe solar cells, achieving 23.42% efficiency in a 4-T tandem configuration. Additionally, using a refractive index matching liquid increases the overall power conversion efficiency (PCE)to 24.2%. This pioneering achievement marks the first instance of a 4-T CdTe/perovskite thin-film tandem solar cell exceeding a PCE of 24.2%, a significant 123.72% increase in overall PCE.more » « less
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Abstract Bandgap gradient is a proven approach for improving the open-circuit voltages (VOCs) in Cu(In,Ga)Se2and Cu(Zn,Sn)Se2thin-film solar cells, but has not been realized in Cd(Se,Te) thin-film solar cells, a leading thin-film solar cell technology in the photovoltaic market. Here, we demonstrate the realization of a bandgap gradient in Cd(Se,Te) thin-film solar cells by introducing a Cd(O,S,Se,Te) region with the same crystal structure of the absorber near the front junction. The formation of such a region is enabled by incorporating oxygenated CdS and CdSe layers. We show that the introduction of the bandgap gradient reduces the hole density in the front junction region and introduces a small spike in the band alignment between this and the absorber regions, effectively suppressing the nonradiative recombination therein and leading to improved VOCs in Cd(Se,Te) solar cells using commercial SnO2buffers. A champion device achieves an efficiency of 20.03% with a VOCof 0.863 V.
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Accepted Manuscript1.0
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