Perovskite ferroelectric thin film as an efficient interface to enhance the photovoltaic characteristics of Si/SnOx heterojunctions

Abstract

The photovoltaic (PV) response of SnO_x/Si heterojunctions (HJs) through the change of the SnO and SnO₂ ratio in the samples that allows us to obtain p- or n-type SnO_x films is investigated in this work. The values of short-circuit photocurrent density (J_sc), open-circuit voltage (V_OC), fill factor (FF) and power conversion efficiency (PCE) are found to be 12.6 mA cm⁻², 0.23 V, 27% and 8.3%, for the p-SnO_x/n-Si HJ and 10.3 mA cm⁻², 0.20 V, 20% and 4.5% for the n-SnO_x/p-Si HJ. The enhanced PV effect observed in the p-SnO_x/n-Si HJs can be attributed to a small band offset between SnO_x and Si, which lowers the diffusion length that can contribute to higher recombination rate and smaller series resistance. Furthermore, the values of J_sc, V_OC, FF and PCE were enhanced up to 30.9 mA cm⁻², −2.0 V, 19% and 10.9%, respectively, through the insertion of a 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃ (BCZT) ferroelectric layer between n-Si and p-SnO_x. The built-in field developed at the Si/BCZT/SiO_x/SnO_x interfaces together with the depolarizing field, provides a favorable electric potential for the separation and further transport of photo generated electron–hole (e–h) pairs. This work provides a viable approach by combining ferroelectrics with p-SnO_x/n-Si HJs for building efficient ferroelectric-based solar cells.