First-principles investigation on adsorption of anchors on two-dimensional halide perovskite material

Anchoring groups are important to immobilize the organic species on emerging energy materials such as the halide perovskite material surfaces to tailor their optoelectronic performance. In this manuscript, we employ first-principles calculations to closely examine the interfacial atomic structures, electronic and optical properties of the anchor/perovskite system, using Cs2PbBr4 as an example. 13 small molecular anchors with various functional anchoring groups, including halogen species (-F, -Cl, -Br and –I) and Lewis acids/bases (–COOH, –NH2, –NO2, –OH, -SH and thiophene) are investigated to comprehensively understand the fundamental interactions between the anchors and the two-dimensional halide perovskite surface. The hydrogen bonds play predominant role in the anchor/perovskite interfacial structural stabilization, while the halogen bonds are suggested to initiate weak interactions. These anchoring groups initiate disparate charge transfer characters at the halide perovskite surface, and the nitrobenzene anchor containing the –NO2 group presents perovskite → molecule surface charge transfer direction while most other anchors cause charge transfer in the reverse direction. In addition, the adsorption of the anchors causes blue-shifts in the UV–vis absorption spectra and optical bleaching effects in the resulting halide perovskite systems. The present study facilitates the fundamental understanding on the basic interactions between the anchoring species and the halide perovskite materials toward the photovoltaic applications.