Atmospherically Processed and Stable Cs-Pb Based Perovskite Solar Cells

Abstract

In this work, a planar heterojunction superstrate n-i-p device based on Zn(O,S) electron transport layer and CsPbI2Br absorber material at 1.93 eV bandgap is presented. The CsPbI2Br films are deposited using a 2-step atmospheric solution deposition process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis spectroscopy and photoluminescence (PL). Best device with an efficiency of 12.34 % and 11.94% in reverse and forward scans respectively and stabilized power output of 12.14 mW/cm2 has been demonstrated via atmospheric solution processing with minimal hysteresis between forward and reverse scans. The devices show voltage dependent current collection as well as light-dark crossover in forward bias. Light soaking tests at 65 °C and 1-sun at Voc, resulted in open-circuit voltage and fill-factor degradation. Electroluminescence (EL) after 100 hours of light soaking shows a reduction in overall EL intensity as well a shift in emission to lower wavelength. The devices exhibit a positive temperature coefficient of about 0.14 %/°C. It is found that Zn(O,S) is a viable alternative electron transport layer to replace TiO2. By replacing methylammonium cation with cesium and addition of Br has improved the stability of the perovskite phase.