Atomistic understanding on molecular halide perovskite/organic/TiO2 interface with bifunctional interfacial modifier: A case study on halogen bond and carboxylic acid group

Organic interfacial modifiers such as the bifunctional molecules have been successfully incorporated in halide perovskite solar cells to boost the optoelectronic performance. However, the atomistic understanding on the structures and properties of the bifunctional molecule-mediated tri-layer perovskite interface remains elusive. In this manuscript, we employ first principles calculations to provide a nanoscopic view on the structures and properties of the perovskite/organic/electron transporting layer (ETL) tri-layer, based on a case study of the MA(4)PbI(6)/bromoacetate/TiO2 system. The calculation reveals the simultaneous coupling of the bifunctional molecule with TiO2 and the halide perovskite material. The organic interfacial modifier is suggested to provide a rich platform for molecular engineering the halide perovskite interface to improve the interfacial charge transfer properties in perovskite solar cells. This work provides a foundation in the convergence to a fundamental understanding of the more sophisticated organic molecule-modified perovskite interfaces in halide perovskite-based optoelectronic devices.