Inverted thermal annealing of perovskite films: a method for enhancing photovoltaic device efficiency

Thermal annealing (TA) plays a vital role in obtaining pinhole-free CH3NH3PbI3 perovskite films with high crystallinity and morphology, which is crucial for achieving high performance for perovskite solar cells (PSCs). In this study, a novel approach named as inverted thermal annealing (ITA) was adopted to dispose the perovskite films. We studied and compared the morphology, surface roughness, and optical and electrical properties of the perovskite films treated by routine TA and ITA, respectively. The perovskite films treated by ITA exhibited higher crystallinity and more favorable morphology and showed stronger of UV light absorption and photoluminescence emission. Therefore, the corresponding PSCs also showed higher average power conversation efficiency (PCE) of 13.49% +/- 0.61% than the devices treated by TA (11.37% +/- 1.15%), and the PCE of the best performing PSCs is as high as 14.10% with an ITA treatment at 100 degrees C. These findings suggest that the ITA treatment is an effective and facile method for preparing high-quality perovskite films and can be used widely for obtaining high performance PSCs.