Search

• The investigation of the defect-related carrier dynamics of CZTSe conducted in this study provided the experimental characterization of the existence of [2Cu Zn − + Sn Zn 2+] defect clusters. From the results, it is important to consider the possibility of factors such as the presence of [2Cu Zn − + Sn Zn 2+] defect clusters when determining the source of the performance degradation of CZTSe solar cells. In this work, a systematic investigation of the effects of point defects on the efficiency of a Cu 2 ZnSnSe 4 (CZTSe) thin film solar cell was conducted using temperature-/power-dependent photoluminescence (PL) and time-resolved photo-luminescence (TRPL). The studied stoichiometric CZTSe absorber layer for a CZTSe solar cell with an efficiency of 4.4 % was prepared using the low-toxicity selenization process. The fitting to the Arrhenius plot and the stretched tail at the long-wavelength side of PL spectrum obtained at 10 K indicated a high concentration of zinc on copper (Cu Zn) point defects. The dispersive-photon-energy-dependent TRPL at 10 K exhibited non-exponential stretched PL decay at all photon energies and, in particular, revealed the highly fluctuating potential of CZTSe that caused carrier localization. This effect was observed to be caused by [2Cu Zn − + Sn Zn 2+] defect clusters, which produce a significant conduction/valence band-edge shift in their vicinity in CZTSe and can cause shunt leakage and an increase in series resistance. This systematic investigation presents the experimental characterization of [2Cu Zn − + Sn Zn 2+] defect clusters and provides perspective to help clarify the performance deterioration of CZTSe solar cells. [ABSTRACT FROM AUTHOR]