12.5% efficiency Cu2ZnSnSe4 kesterite thin-film solar cells enabled by engineering of local chemical environment
Jianjun Li a, Xiaojing Hao a, Martin A. gREEN a
a The University of New South Wales, Australia, Kensington NSW 2052, Australia, Kensington, Australia
Online Conference
Proceedings of International Conference on Advanced Light Absorbing Materials for Next Generation Photovoltaics (ABSOGEN)
Online, Spain, 2020 November 17th - 18th
Organizers: Hongxia Wang, Xiaojing Hao and Lydia Wong
Oral, Jianjun Li, presentation 020
DOI: https://doi.org/10.29363/nanoge.absogen.2020.020
Publication date: 6th November 2020

Kesterite-based Cu2ZnSn(S,Se)4 semiconductors are emerging as promising materials for low-cost, environment-benign, and high-efficiency thin-film photovoltaics. However, the current state-of-the-art Cu2ZnSn(S,Se)4 devices suffer from cation-disordering defects and defect clusters, which generally result in severe potential fluctuation, low minority carrier lifetime, and ultimately unsatisfactory performance. Herein, we report critical growth conditions for obtaining high-quality Cu2ZnSnSe4 absorber layers with the formation of detrimental intrinsic defects largely suppressed. By controlling the oxidation states of cations and modifying the local chemical composition, we essentially modify the local chemical environment during the synthesis of kesterite phase, thereby effectively suppressing detrimental intrinsic defects and activating desirable shallow acceptor Cu vacancies. Consequently, we demonstrate a confirmed 12.5% efficiency with high VOC of 491 mV, which is the new record efficiency of pure-selenide Cu2ZnSnSe4 cells with lowest VOC deficit in the kesterite family by Eg/q-Voc. These encouraging results demonstrate an essential route to overcome the long-standing challenge of defect control in kesterite semiconductors, which may also be generally applicable to other multinary compound semiconductors.

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