PbI2 platelets for inverted planar organolead Halide Perovskite solar cells via ultrasonic spray deposition

Morphology control of organometal halide perovskite thin films is of importance in order to develop highly efficient perovskite solar cells. Here, a seeded growth method is introduced for the first time to deposit lead iodide (PbI2) with platelet structures on an organic hole transporting layer PEDOT:PSS. The PbI2 platelets are effectively converted into perovskite thin film when subject to sprayed droplets of methylammonium in isopropyl alcohol. Compared with evaporated compact PbI2 layers, the PbI2 platelet enables a thicker perovskite thin film to be formed with less unreacted PbI2. Using this technique, we have achieved pinhole-free and uniform perovskite thin film with root-mean-square roughness of 12.81 nm, and an average solar cell efficiency higher than those fabricated from compact PbI2 thin film.