Impact of Diethyl Ether Dripping Delay Time on the Electronic Structure of Methylammonium Lead Triiodide Perovskite Film

Recently, organolead halide perovskites have demonstrated excellent performance in solar cell application. For efficient perovskite solar cells, a uniform and dense perovskite film should be fabricated. A popular method to obtain such film is anti-solvent dripping during the intermediate phase formation. This dripping should be performed at the certain delay time after the spin start. The change in delay time could impact defect formation, significantly varying the electronic structure. The electronic structure of a perovskite film plays a crucial role in the charge transport and recombination in the devices. Thus, the determination of the electronic structure is of major significance to analyze the device performance. In this study, we investigated the electronic structure of methylammonium lead triiodide films fabricated with the different delay time of diethyl ether (DE) dripping. The core level and the valence band were measured using X-ray and ultraviolet photoelectron spectroscopy. As the DE dripping delay time increases, the I/N ratio increases while the work function decreases. This would be attributed to the n-doping effect by the positively charged I-interstitial defect formation.