Effect of anti-solvent chlorobenzene on bottom micro-porous structure of perovskite light-absorbing layer

•Effect of anti-solvent on bottom micro-pore of perovskite layer is observed.•Delay time effect on the feature size is revealed by using statistics analysis.•Formation mechanism based on density and vapor-presure of anti-solvent is proposed. Anti-solvent technology plays an important role in one-step solution-processed spin-coating method for perovskite solar cells. In this article, we studied the effect of chlorobenzene as anti-solvent added at different time during one-step spin-coating for thin film of perovskite. We found that dropping chlorobenzene at different time would affect the amount of chlorobenzene entering the precursor solution, resulting in the growth of microporous structures in the perovskite layer. Early or late dropping of chlorobenzene produced a microporous structure layer. Although the top view of the perovskite layer was complete, a cross-sectional perspective shows the presence of micro-porous structures in the perovskite layer. When the chlorobenzene was dripped at 25 s, it was seen from the PL spectrum that the micro-porous structure at the bottom of the perovskite layer was less porous and the film quality was better. Moreover, the effect of dropping of chlorobenzene at different time on the characteristic size of the micro-porous structure at the bottom of the perovskite film was revealed by statistical analysis. A possible mechanism on the formation of the bottom micro-porous structure of perovskite film was proposed. Our work suggests the effect of one-step solution-processed spin-coating method for structure of perovskite layer by using chlorobenzene as an anti-solvent.