Solution-induced morphology change of organic-inorganic hybrid perovskite films for high efficiency inverted planar heterojunction solar cells

Planar heterojunction perovskite solar cell promises low cost solution manufactured solar cells with the efficiency of single crystal silicon cells. However, it is still a great challenge to fabricate high quality perovskite films by solution method. Here, we demonstrate a simple method to control the morphology of perovskite film deposited on the top of a PEDOT: PSS coated ITO glass. The key to the process is to induce a change at the stage of the nucleation of intermediate phase, leading to the homogenous high density nucleation of the particles without preferred orientation instead of the sparse nucleation of the needle shaped crystals by a solvent treatment using a solvent which is miscible with the solvent of the perovskite precursor solution, but less soluble to the precursors of PbI₂ and CH₃NH₃I. The morphology of the intermediate phase determines the morphology of final perovskite film. Planar inverted heterojunction perovskite solar cells fabricated using the perovskite films deposited by the method as the absorb layer show a reproducible efficiency of 13.1%.