Suppressed Halide Segregation and Defects in Wide Bandgap Perovskite Solar Cells Enabled by Doping Organic Bromide Salt with Moderate Chain Length

Abstract

Wide bandgap perovskite solar cells have gained extensive attention due to their complementary absorption to fabricate high performance tandem solar cells with low bandgap absorbers, whereas the open-circuit voltage (VOC) loss caused by halide segregation and defects is one of the main issues hindering their performance. Herein, we report a strategy of adding organic bromide salts with different chain lengths including phenylammonium bromide (PhABr), phenmethylammonium bromide (PMABr) and phenethylammonium bromide (PEABr) into perovskite precursor to suppress the formation of iodide-rich phases and passivate the defects in perovskite films. It is shown that PMABr, which possesses moderate chain length, performs best in improving device performance. The power conversion efficiency (PCE) of 17.32% with enhanced VOC have been achieved, which are much better than these of the standard device (15.72%) and the devices with PhABr (15.98%) or PEABr additives (16.83%). As the chain length is a common variable among different additives, so the results obtained in this work show that it shall be considered in screening the additives.