Evolution of Hole Transport/Perovskite Layer Properties with Au Evaporation Condition in a Perovskite Solar Cell

Changes in the properties of the hole transport layer (HTL) and the perovskite layer in a perovskite solar sell (PSC) were observed under various Au thermal evaporation conditions. We employed a conventional thermal evaporator with a distance of 30 cm between the source and substrate in a vacuum of 6 x 10(-6) torr. We prepared 70 nm-thick Au layers on PSCs by varying the evaporation condition: 60 W-90 min, 70 W-60 min, 80 W-25 min, 90 W-10 min, and 100 W-7 min. Subsequently, the photovoltaic properties of the PSC were measured for each deposition condition. Also, the microstructure of the HTL/perovskite was observed using a scanning electron microscope (SEM) and electron probe x-ray micro-analyzer (EPMA) after the Au layer was selectively removed. The most outstanding energy conversion efficiency (ECE) was measured for the 80 W-25 min condition. The ECE was extremely low at relatively low power-long time (60 W-90 min, 70 W-60 min) conditions, due to contamination of the HTL and the perovskite layers during the Au evaporation. The contamination was confirmed from the SEM and EPMA investigations. Moreover, even with high powered-short time (90 W-10 min, 100 W-7 min) conditions, the HTL underlayer of the electrode was damaged due to the high deposition energy.