Multistep spin-spray deposition of large-grain-size CH3NH3PbI3 with bilayer structure for conductive-carbon-based perovskite solar cells

摘要

Large-grain-size and void-free CH3NH3PbI3 films with bilayer structure are fabricated by spin-coating a PbI2 layer onto a mesoporous TiO2 layer and sequentially spraying CH3NH3I (methylammonium iodide, MAI) multilayers. The sprayer is controlled by a homemade three-axis computer numerical control machine; thus, the substrates are coated by successive parallel passes achieved by moving the nozzle. Spray deposition at the optimal spray rate and substrate temperature produces a large-grain-size and void-free methylammonium lead iodide (MAPbI(3)) bilayer structure. The mesoporous TiO2 layer plays an important role in electron transport by preventing the return of electrons to the perovskite layer and decreasing the contact resistance at the perovskite/compact TiO2/fluorine tin oxide interface. When the films are incorporated into a solar cell device with a conductive carbon counter electrode, a maximum power conversion efficiency of 10.58% is realised.