Effects of composition and thermal treatment on VOC-limiting defects in single-crystalline Cu2ZnSnSe4 solar cells
Date
2021-11-19
Journal Title
Journal ISSN
Volume Title
Publisher
Progress in Photovoltaics
Abstract
Single-crystalline Cu2ZnSnSe4 (CZTSe) solar cells with open circuit voltages reaching 500 mV are achieved through a combination of composition control and a low-temperature thermal ordering treatment. A comparison of the device results for Cu-poor CZTSe with Cu/Zn + Sn ratios of 0.77 and 0.86 is presented with and without the implementation of a 130°C absorber annealing treatment. An increase in bandgap energy is observed via external quantum efficiency measurements with both the decrease in Cu content and the implementation of the order anneal, the latter of which also leads to a decrease in Urbach energy. Defect characterization performed with admittance spectroscopy on devices is demonstrated as insufficient because of low-temperature current barriers. Photoluminescence (PL) on crystal surfaces however enables a qualitative comparison of the defect landscape between crystal compositions and annealing treatments. Both a highly compensated and a lightly doped defect model are used to fit PL as a function of laser fluence to identify defects contributing to each observed recombination channel. The PL signatures attributed to the ZnSn defect become unresolvable with a decrease in Cu/Zn + Sn ratio from 0.86 to 0.77. Furthermore, a decrease in Cu–Zn disorder is observed upon the implementation of the annealing treatment through both a comparison of potential fluctuation depths and of both PL models.
Description
This is the peer reviewed version of the following article: Lloyd, MA, Ma, X, Kuba, AG, McCandless, BE, Doty, MF, Birkmire, R. Effects of composition and thermal treatment on VOC-limiting defects in single-crystalline Cu2ZnSnSe4 solar cells. Prog Photovolt Res Appl. 2021; 1- 15. doi:10.1002/pip.3516, which has been published in final form at https://doi.org/10.1002/pip.3516. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.
This article was originally published in Progress in Photovoltaics. The version of record is available at: https://doi.org/10.1002/pip.3516
Keywords
defects, kesterites, photoluminescence, single crystals, solar cells
Citation
Lloyd, MA, Ma, X, Kuba, AG, McCandless, BE, Doty, MF, Birkmire, R. Effects of composition and thermal treatment on VOC-limiting defects in single-crystalline Cu2ZnSnSe4 solar cells. Prog Photovolt Res Appl. 2021; 1- 15. doi:10.1002/pip.3516