Perovskite ferroelectric thin film as an efficient interface to enhance the photovoltaic characteristics of Si/SnOx heterojunctions†
The photovoltaic (PV) response of SnOx/Si heterojunctions (HJs) through the change of the SnO and SnO2 ratio in the samples that allows us to obtain p- or n-type SnOx films is investigated in this work. The values of short-circuit photocurrent density (Jsc), open-circuit voltage (VOC), 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-SnOx/n-Si HJ and 10.3 mA cm−2, 0.20 V, 20% and 4.5% for the n-SnOx/p-Si HJ. The enhanced PV effect observed in the p-SnOx/n-Si HJs can be attributed to a small band offset between SnOx and Si, which lowers the diffusion length that can contribute to higher recombination rate and smaller series resistance. Furthermore, the values of Jsc, VOC, 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(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT) ferroelectric layer between n-Si and p-SnOx. The built-in field developed at the Si/BCZT/SiOx/SnOx 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-SnOx/n-Si HJs for building efficient ferroelectric-based solar cells.