Enhanced TiO2/MAPbI(3) Electronic Coupling by Interface Modification with PbI2

We report a combined experimental and computational investigation to elucidate the effect of PbI2 on the electronic properties of the TiO2/methylammonium lead-iodide (MAPbI3) perovskite interface. We propose that excess PbI2 from the precursor solution or from a TiO2 pre-treatment may be predominantly located at the interface with the semiconducting oxide, enhancing the interfacial electronic coupling and favorably modifying the electronic energy levels landscape at the interface. This is in turn found to facilitate electron transfer from the MAPbI3 perovskite to the TiO2 electron transport layer as revealed by a fast quenching in the photoluminescence dynamics, confirming the beneficial role of PbI2 at the interface.