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Suppressed Deep Traps and Bandgap Fluctuations in Cu 2 CdSnS 4 Solar Cells with ≈8% Efficiency
Author(s) -
Hadke Shreyash,
Levcenko Sergiu,
Sai Gautam Gopalakrishnan,
Hages Charles J.,
Márquez José A.,
IzquierdoRoca Victor,
Carter Emily A.,
Unold Thomas,
Wong Lydia H.
Publication year - 2019
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201902509
Subject(s) - materials science , band gap , limiting , solar cell , energy conversion efficiency , solar cell efficiency , zinc , optoelectronics , nanotechnology , metallurgy , mechanical engineering , engineering
The identification of performance‐limiting factors is a crucial step in the development of solar cell technologies. Cu 2 ZnSn(S,Se) 4 ‐based solar cells have shown promising power conversion efficiencies in recent years, but their performance remains inferior compared to other thin‐film solar cells. Moreover, the fundamental material characteristics that contribute to this inferior performance are unclear. In this paper, the performance‐limiting role of deep‐trap‐level‐inducing 2Cu Zn +Sn Zn defect clusters is revealed by comparing the defect formation energies and optoelectronic characteristics of Cu 2 ZnSnS 4 and Cu 2 CdSnS 4 . It is shown that these deleterious defect clusters can be suppressed by substituting Zn with Cd in a Cu‐poor compositional region. The substitution of Zn with Cd also significantly reduces the bandgap fluctuations, despite the similarity in the formation energy of the Cu Zn +Zn Cu and Cu Cd +Cd Cu antisites. Detailed investigation of the Cu 2 CdSnS 4 series with varying Cu/[Cd+Sn] ratios highlights the importance of Cu‐poor composition, presumably via the presence of V Cu , in improving the optoelectronic properties of the cation‐substituted absorber. Finally, a 7.96% efficient Cu 2 CdSnS 4 solar cell is demonstrated, which shows the highest efficiency among fully cation‐substituted absorbers based on Cu 2 ZnSnS 4 .

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