Insights into the impact of defect states and temperature on the performance of kesterite-based thin-film solar cells

Abstract

In this study, we explore the influence of defect states density and operating temperatures on the performance of kesterite-based (CZT(S,Se)) solar cells such as CZTS, CZTSe, and CZTSSe. SCAPS codes were used as a constructive technique in modeling all structures. The CZT(S,Se) structures were modified by incorporating a p-Mo(S,Se)2 interfacial layer between the back contact and the absorber. Interestingly, only a 100 nm thick layer of p-Mo(S,Se)2 can establish a quasi-ohmic configuration at a CZT(S,Se)/Mo heterojunction, which was demonstrated by an increase in the slope of the J-V characteristics. In the active layer region, a series of systematic simulations were conducted depicting the response of CZTSSe/MoSSe structures to defect density states ranging from 1013 cm-3 to 1017 cm-3. The recombination behavior of CZTSSe/MoSSe solar cells is significantly superior to those made of CZTS/MoS2 or CZTSe/MoSe2, with a minimum increase in recombination current of 2.03 mA/cm2. The increased recombination rates are attributed to a shorter minority carrier lifetime at the buffer-absorber interface due to a reduced diffusion length between electrons and holes. Additionally, the photovoltaic parameters of the CZT(S,Se) structures were examined over a wide temperature range, from 275 K to 475 K, including open-circuit voltage (Voc), short circuit current (Jsc), fill factor (FF), and power conversion efficiency (PCE). A CZTS/MoS2-based structure exhibited the most stable performance at elevated temperatures up to 395 K with minimum degradation in PCE of approximately 2% compared to other solar cells. As a result, the voltage variation to temperature coefficients obtained for the CZTS and CZTSe solar cells were − 0.75 mV/K and − 1.2 mV/K, respectively. These findings support the use of CZTS/MoS2 structures in the development of photovoltaic modules that are capable of operating at high temperatures.