Boosting Radiation of Stacked Halide Layer for Perovskite Solar Cells With Efficiency Over 25%

Although halide perovskite solar cells (PSCs) have shown tremendous progress in device performance, state-of-the-art of PSCs is still far below the theoretical efficiency. To further reach the theoretical limit, it is essential to maximize radiative recombination of a light-absorbing halide perovskite layer stacked with charge transport layers rather than solely as a halide layer. Here, we provide a holistic approach introducing potassium hexafluorophosphate salts as a multifunctional agent to treat the SnO2/perovskite interface and bulk halide layer, boosting radiation of the stacked halide layer. We found that controlling the SnO2/perovskite interface is a main factor to boost radiation in full device stack. On combining interface and bulk engineering, the FTO/SnO2/halide structure and full device stack exhibited an enhanced external photoluminescence quantum efficiency (PLQE) of 45.44% and 15.57%, respectively. As a result, the device combined with the interface and bulk engineering showed an improved reverse-forward average power conversion efficiency (PCE) of 25.64% and certified quasi-steady-state (QSS) efficiency of 25.06%. The certified open-circuit voltage (Voc) of 1.18V is 94.93% of the radiative limit Voc of 1.243V, the highest value among certified QSS Voc of PSCs. Moreover, the device maintained 80% of its initial PCE for 500 hours under 10% relative humidity at 85℃ without any encapsulation. This holistic approach provides a promising direction for reaching the theoretical limit of PSCs by boosting radiation.