Ge-alloying-regulated band-edge dynamics suppress nonradiative recombination in kesterite Cu₂Zn(Ge_xSn_1-x)S₄.

Authors

Xinwei Guo, Zuyun Chen, Xuemin Hu, Chun Wang, Shengli Zhang, Wenhan Zhou

Published in

Physical chemistry chemical physics : PCCP. Sep 18, 2026. Epub Sep 18, 2026.

Abstract

Cu₂ZnSn(S,Se)₄ kesterite photovoltaics suffer from severe voltage losses associated with cation disorder, band-tail fluctuations, and nonradiative carrier recombination. Ge-alloying has been reported to improve absorber quality and reduce recombination losses, but the underlying carrier-dynamics mechanism remains unclear. Here, density functional theory and nonadiabatic molecular dynamics are used to investigate Cu₂Zn(Ge_xSn_1-x)S₄ in Cu/Zn ordered and disordered configurations. The calculations show that Cu/Zn disorder introduces local structural distortion, electrostatic perturbations, and low-frequency anharmonic phonon channels, thereby enhancing electron-vibrational coupling and accelerating nonradiative recombination. Because the conduction band minimum is dominated by Ge/Sn-s and S-3p antibonding states, Ge/Sn-S bond fluctuations regulate conduction band-edge dynamics more strongly than the Cu-3d/S-3p-derived valence band maximum. Increasing Ge content generally widens the bandgap and reduces nonadiabatic coupling, whereas the carrier lifetime varies nonmonotonically owing to the coupled effects of band-edge fluctuations, phonon spectral density, electronic delocalization, and dephasing-mediated dynamics. These results provide a microscopic explanation for Ge-alloying-suppressed recombination in kesterite photovoltaics.

PMID:
42758028
Bibliographic data and abstract were imported from PubMed on 18 Sep 2026.

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