Emerging strategies towards ambient condition fabrication of perovskite solar cells

The power conversion efficiency of perovskite solar cells (PSCs) has remarkably increased, in just a few years, from 3.8 to 22.7%, due to the excellent properties of organometal-halide perovskite, such as strong and broad optical absorption from visible to near infrared, high electron and hole diffusion length and a low surface recombination velocity. Nevertheless, PSCs are susceptible to oxygen and water, because of a degradation pathway leading to the formation of lead iodide, methylammonium and hydrogen iodide. For this reason, perovskite materials require high temperature and glove-box synthetic conditions, thus hindering large-scale applications. During last year, a few efforts have been made in the development of ambient condition fabrication strategies, such as thermal engineering and the use of anti-solvents. In the first case, the substrate TiO2 is pre-heated at low temperature before spin-coating deposition of perovskite precursors. This ensures phase purity and a pinhole-free morphology, with a PCE reaching 12%. In the second case, the use of anti-solvents reduces the solubility of perovskite precursors, thereby promoting fast nucleation and rapid crystallization. In this way, the effect of air-moisture is less relevant. In conclusion, the fabrication of PSCs in open air atmospheric conditions is challenging, but necessary for photovoltaic application of perovskite materials.