The poor stability of perovskite solar cells that are based on methylammonium (MA)‐containing compositions has triggered immense interest in the development of MA‐free alternatives such as the double‐cation mixed‐halide Cs x FA1–x Pb(I1–x  + Br x )3 composition (CsFA perovskites). Although efficient solar cells based on this composition have been reported, many aspects related to the film formation of CsFA perovskites remain unclear. Herein, the influence of the antisolvent application rate on the properties and device performance of MA‐free perovskite solar cells are investigated. It is found that when applied slowly, all six of the investigated antisolvents result in high‐quality films and devices reaching a maximum power conversion efficiency of 20.7%. However, fast application leads to incomplete film coverage, and consequently no functional solar cells, for three of these antisolvents. It is demonstrated that this is related to the inefficacy of these antisolvents in triggering the crystallization of the perovskite layer and a simple test is offered that can aid researchers to identify whether other antisolvents will favor fast or slow antisolvent application.

The use of antisolvents during the fabrication of solution-processed lead halide perovskite layers is increasingly common. Usually, the antisolvent is applied by pipetting during the spin-coating process, which often irreversibly...

Metal halide perovskites are an emerging class of crystalline semiconductors of great interest for application in optoelectronics. Their properties are dictated not only by their composition, but also by their crystalline structure and microstructure. While significant efforts are dedicated to the development of strategies for microstructural control, significantly less is known about the processes that govern the formation of their crystalline structure in thin films, in particular in the context of crystalline orientation. This work investigates the formation of highly oriented triple cation perovskite films fabricated by utilizing a range of alcohols as an antisolvent. Examining the film formation by in situ grazing-incidence wide-angle X-ray scattering reveals the presence of a short-lived highly oriented crystalline intermediate, which is identified as FAI-PbI 2 -xDMSO. The intermediate phase templates the crystallization of the perovskite layer, resulting in highly oriented perovskite layers. The formation of this dimethylsulfoxide (DMSO) containing intermediate is triggered by the selective removal of N,N-dimethylformamide (DMF) when alcohols are used as an antisolvent, consequently leading to differing degrees of orientation depending on the antisolvent properties. Finally, this work demonstrates that photovoltaic devices fabricated from the highly oriented films, are superior to those with a random polycrystalline structure in terms of both performance and stability.

This feature article outlines the impact of solvent–antisolvent interactions on the film formation processes of metal halide perovskites.