Photovoltaic Device with over 5% Efficiency Based on an n‐Type Ag₂ZnSnSe₄ Absorber

Abstract

The kesterite material Cu 2 ZnSn(S,Se) 4 (CZTSSe) is an attractive earth-abundant semiconductor for photovoltaics. However, the power conversion efficiency is limited by a large density of I-II antisite defects, which cause severe band tailing and open-circuit voltage loss. Ag 2 ZnSnSe 4 (AZTSe) is a promising alternative to CZTSSe with a substantially lower I-II antisite defect density and smaller band tailing. AZTSe is weakly n-type, and this study reports for the first time on how the carrier density is impacted by stoichiometry. This study presents the first-ever photovoltaic device based on AZTSe, which exhibits an efficiency of 5.2%, which is the highest value reported for an n-type thin-film absorber. Due to the weakly n-type nature of the absorber, a new architecture is employed (SnO:F/AZTSe/MoO 3 /ITO) to replace conventional contacts and buffer materials. Using this platform, it is shown that the band tailing parameter in AZTSe more closely resembles that of CIGSe than CZTSSe, underscoring the strong promise of this absorber. In demonstrating the ability to collect photo-generated carriers from AZTSe, this study paves the way for novel thin-film heterojunction This article is protected by copyright. All rights reserved. architectures where light absorption in the n-type device layer can supplement absorption in the ptype layer as opposed to producing a net optical loss.

Photoelectrochemical performances of kesterite Ag 2 ZnSnSe 4 photoelectrodes in the salt-water and water solutions

“…The values of carrier concentrations for all samples are negative, which indicate that the samples are the n-type semiconductors. The results agree well with that reported by Gershon et al [22] and the conduction type of Ag 2 ZnSnS 4 samples [34,35] . Yuan et al [35] systematically investigated the defects formed in the quaternary Cu-based and Ag-based kesterite metal sulfide compounds using density function theory calculations.…”

Suppressed Deep Traps and Bandgap Fluctuations in Cu2CdSnS4 Solar Cells with ≈8% Efficiency

“…Energy Mater. 2019, 9,1902509 [53] Sputtering and e-beam evaporation Ag 2 ZnSnSe 4 5.2 [54] Coevaporation Cu 2 BaSn(S,Se) 4 5.2 [9] Cosputtering Cu 2 FeSnS 4 2.9 [55] SILAR efficiency Cu 2 CdSnS 4 , we show that cation substitution not only can be used to improve the performance of kesterites but also to systematically study their performance-limiting factors. Finally, the suppressed deep defects and bandgap fluctuations lead to a promising 7.96% efficient Cu 2 CdSnS 4 , which could be further improved with device optimization.…”

Theoretical Design of the Absorber for Intermediate Band Solar Cells from Group‐IV (Si, Ge, and Sn)‐Doped AgAlSe2

“…On the other side, Ag‐based compounds have the lower valence band position than Cu‐based compounds because of the lower d‐orbital energy and longer bond length. Some Ag‐based compounds, like AgInSe 2 , AgAlTe 2 , AgGaTe 2 , and Ag 2 ZnSnSe 4 , have also been studied as the absorber for the single band gap solar cell. The n‐type conductivity has been reported in these Ag‐based compounds, which make them have the ability to keep the IB half‐filled.…”

“…Some Ag‐based compounds, like AgInSe 2 , AgAlTe 2 , AgGaTe 2 , and Ag 2 ZnSnSe 4 , have also been studied as the absorber for the single band gap solar cell. The n‐type conductivity has been reported in these Ag‐based compounds, which make them have the ability to keep the IB half‐filled. Ag‐based chalcopyrite compound like AgAlSe 2 (2.55 eV) with optimum band gap width should be the suitable candidate for the host of IBSC.…”