Highly efficient double-side-passivated perovskite solar cells for reduced degradation and low photovoltage loss

Abstract

Hybrid metal halide perovskite solar cells (PSCs) are the most promising candidates to share the future energy market with silicon solar cells thanks to their excellent photovoltaic (PV) properties in single junction and tandem applications. Although PSCs are already highly efficient, their performance can be further improved by passivating the perovskite boundaries and improving current-voltage hysteresis. Here, we implement a double-sided passivation approach to enhance the performance of n-i-p structured PSCs, showing how passivating on either side improves cell performance. The electron-collecting side was passivated with biphenyl-4,4 -dicarboxylic acid (BPDC), and n-octyl ammonium bromide was used to passivate the hole-collecting side. The power conversion efficiency of the champion cell improved from 18.7 % for control to 20.9 % when double-sided passivation was implemented. Surface imaging showed how the surface boundaries improved following passivation, resulting in better open circuit voltages (VOC) and fill factors. In addition, passivation creates a barrier for ion migration, improving J-V hysteresis and stability in the process. The champion cell displayed a VOC of 1192 mV with double-sided passivation, incurring only ∼390 mV loss, thereby achieving a high VOC with a mid-bandgap perovskite. Preliminary degradation testing in ambient conditions shows that double-sided passivation also improves the stability of the cells by impeding ion migration.