Hole blocking PbI₂/CH₃NH₃PbI₃ interface

Modulated charge separation across (MO)/CH3NH3PbI3 and (MO)/PbI2/CH3NH3PbI3 (MO = TiO2, MoO3) interfaces was investigated by surface photovoltage (SPV) spectroscopy. Perovskite layers were deposited by solution-based one-step preparation and two-step preparation methods. An unreacted PbI2 layer remained at the interface between the metal oxide and CH3NH3PbI3 for two-step preparation. For the two-step preparation on TiO2, the SPV signal related to absorption in CH3NH3PbI3 increased in comparison to the one-step preparation due to electron transfer from CH3NH3PbI3 via PbI2 into TiO2 whereas the SPV signal related to defect transitions decreased. For the one-step preparation on MoO3, holes photogenerated in CH3NH3PbI3 recombined with electrons in MoO3. In contrast, a hole transfer from CH3NH3PbI3 towards MoO3 was blocked by the PbI2 interlayer for the two-step preparation on MoO3. (© 2014 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)