A First-Principles Study of Anchoring Group Effects of Self-Assembled Hole Transport Materials for Perovskite Solar Cells.

Self-assembled molecules (SAMs) have been widely used as hole-selective layers for inverted perovskite solar cells. In this work, eight hole-selective compounds containing different acidic anchoring groups are designed. Their anchoring effects on the typical indium tin oxide (ITO) surface, including both absorption structure and electron states, are systematically studied using the first-principles calculation method based on density functional theory. Among the eight anchoring groups, silicic acid, cyanoacetic acid, cyanophosphoric acid, and phosphoric acid are the strongest in the absorption ability, and it is found that an increase in the number of dehydrogenations of the anchoring groups leads to an increase in the adsorption capacity of SAMs. In addition, the adsorption of SAMs can also cause the change of ITO's work function, providing a potential strategy to modify the work function of transparent conductive oxide substrate by anchoring group engineering. The Ab Initio Molecular Dynamics simulation at high temperature reveals that the silicic acid and phosphoric acid anchoring groups have the best thermal stability. Study of SAMs/FAPbI3 adsorption system reveals that cyanoacetic acid anchoring group has the largest adsorption energy. This work shows the great potential of precisely designed self-assembled molecules for high-performance perovskite solar cells.