Thermal degradation and defect growth in CZTSSe photovoltaic devices

Abstract

Thermal degradation of Kesterite thin film solar cells (CdS/CZTSSe) has been studied using three different time-dependent models which formulate the defect growth kinetics within the depletion width of CZTSSe/CdS junction. Generation and annihilation of a shallow acceptor defect at 0.55 eV under the stress of heating at 400 °C for 1000 h have been modeled. Three cases were modeled for defect growth rate by relating defect generation to electrons and hole density increment linearly (n) or quadratically (np or n2). The non-radiative recombination has been modeled for the three models and enabled the calculation of heat generation across the depletion width. The heat generation was also mapped through a coupled optical-electrical-thermal model in COMSOL for defect growth models at elevated stressing time. Heat generation is then stronger for the n-model and rises to double times higher by increasing the stressing time to 1000 h.