Perovskite Solar Cells
Two-dimensional, 2D, perovskites, with a formula of (RNH3)2MAn-1PbnI3n+1, have shown impressive photovoltaic device efficiency with improved stability by a hot-casting method. However, the reported hot-casting method, that is, casting perovskite precursors on substrates preheated to 150 °C, is quite finicky and hard to be reproduced to generate similar results as reported.
Published in ACS Applied Materials & Interfaces, researchers in the the You Group, led by Dr. Liang Yan, have devised a low temperature, additive-free, and fast processing method to fabricate butyl ammonium based 2D perovskites solar cells. This new method is reaching similarly high efficiency, ∼12%, when processed in ambient condition with 45% relative humidity, yet with excellent reproducibility.
The new method includes coating the precursor solution onto the substrate kept at room temperature, followed by post-annealing the half-finished device at a given temperature for a short period of time. Experimental evidences indicated that the 2D perovskite made by the post-annealing method exhibited similar vertical phase separation as the hot-casting method. The Moran Group conducted further TA measurement, and the data suggested that the energy transfer mechanism, at least in short time scale, played an important role in achieving the observed high power conversion efficiency for these 2D perovskites-based solar cells. In addition, this new post-annealing method was generally applicable to incorporate other large organic cations into 2D perovskites to generate efficient solar cells.