Understanding the crystallization of triple-cation perovskites assisted by mixed antisolvents for improved solar cell device performance

In perovskite solar cells, the active perovskite layer is crucial in influencing the solar cell's efficiency. Crack-free perovskite films with enlarged grain size are essential for a highly efficient solar cell. Triple-cation perovskite (TC-PVS) mainly relies on solvent–antisolvent engineering for achieving good crystal growth and enlarged grains. In recent years, research has been done involving antisolvents in TC-PVS. The Antisolvent-Assisted Crystallization (ASAC) method is considered one such way to obtain improved film quality. However, the perovskite films prepared by the ASAC method still suffer from low coverage and rapid degradation. Thus, the choice of antisolvent or mixture of antisolvents can be crucial in effectively precipitating the perovskite and demonstrating high efficiency. To achieve an ideal choice of antisolvents, we have examined a mixture consisting of Ethyl Acetate (EA) with Chlorobenzene (CB) and EA with Isopropyl Alcohol (IPA) in different ratios for the fabrication of the perovskite layer. In this case, EA acted as a solvent that assists in dissolving the excess perovskite precursor due to its polar nature; and IPA and CB enhanced crystallization by reducing the solubility of the perovskite. The device fabricated using 25% CB in EA mixture of antisolvents gave an improved efficiency of 11% compared to those prepared using only EA, CB, and IPA individually. High-quality, crack-free perovskite layers with enhanced grain sizes are attained from using mixtures of CB in EA, which resulted in improved photovoltaic properties.