Schmeißer, D.; Henkel, K.; Pozarowska, E.; Kegelmann, L.; Tsud, N.; Kot, M.: Point Defect-Mediated Interface Formation and Appearance of a Cooper Minimum for AlOx Atomic-Layer-Deposited Films on CH3NH3PbI3. The Journal of Physical Chemistry C 123 (2019), p. 23352-23360

We report on the interaction of CH3NH3PbI3 substrates with AlOx films prepared by atomic layer deposition at room temperature. We use synchrotron radiation-based photoemission spectroscopy and study the Pb 4f, I 3d, and Al 2p core levels as well as the corresponding valence band states (Pb 5d and O 2p). A Cooper minimum is observed for both the Pb 5d and O 2p states, and it indicates that the bonding at the interface must be covalent. We focus on the electronic properties of the substrate and its interface and identify a delicate charge balance between polaronic and excitonic states in MAPI and AlOx. The perovskite vacancy sites, identified by changes in the core-level intensities, mediate the charge balance and covalent interaction.