Interfacial Bonding and Electronic Structure between Copper Thiocyanate and Hybrid Organohalide Lead Perovskites for Photovoltaic Application.

Interface engineering of halide perovskite solar-cell device layers has been showing potential for the enhancement of efficiency and stability. The replacement of spiro-OMeTAD with cheap hole extraction layer CuSCN has emerged as one effective method for the long-term large-scale application. To clarify the interfacial mechanism between the halide perovskite layer and the CuSCN layer, first-principles calculations were performed. An interface-induced electrostatic potential increase and electron-hole excitation were observed at the interfaces. A Cu-I bond and a Pb-N bond were formed at the interface. The MAI interface exhibited a larger ionic displacement and a higher interface-induced potential than the PbI interface. Strong hybridization among Cu 4d, I 5p, N 2p, and Pb 6p orbitals at the interface was found to be the origin of the electron-hole excitation, interface reconstruction, electron charge redistribution, and stability enhancement.