Enhancing the Durability and Carrier Selectivity of Perovskite Solar Cells Using a Blend Interlayer.

A mechanically and thermally stable and electron-selective ZnO/CH3 NH3 PbI3 interface is created via hybridization of a polar insulating polymer, poly(ethylene glycol) (PEG), into ZnO nanoparticles (NPs). PEG successfully passivates the oxygen defects on ZnO and prevents direct contact between CH3 NH3 PbI3 and defects on ZnO. A uniform CH3 NH3 PbI3 film is formed on a soft ZnO:PEG layer after dispersion of the residual stress from the volume expansion during CH3 NH3 PbI3 conversion. PEG also increases the work of adhesion of the CH3 NH3 PbI3 film on the ZnO:PEG layer and holds the CH3 NH3 PbI3 film with hydrogen bonding. Furthermore, PEG tailors the interfacial electronic structure of ZnO, reducing the electron affinity of ZnO. As a result, a selective electron-collection cathode is formed with a reduced electron affinity and a deep-lying valence band of ZnO, which significantly enhances the carrier lifetime (473 μs) and photovoltaic performance (15.5%). The mechanically and electrically durable ZnO:PEG/CH3 NH3 PbI3 interface maintains the sustainable performance of the solar cells over 1 year. A soft and durable cathodic interface via PEG hybridization in a ZnO layer is an effective strategy toward flexible electronics and commercialization of the perovskite solar cells.