Post-Assembled Dipole Benzoic Acids Modified Me-4PACz for Efficient and Stable Inverted Perovskite Solar Cells

Abstract

Self-assembled monolayers (SAMs), particularly those molecules composed of carbazole and phosphonic acid, are widely employed as effective hole-selective layer (HSL) in inverted perovskite solar cells (PSCs). However, the insufficient chemical bond formation with metal oxides (ITO) and self-aggregation in solvents of carbazole phosphonic acid SAM led to non-uniform HSL, which in turn affect power conversion efficiency (PCE) and stability of the PSCs. Herein, a series of benzoic acid materials (BAs), including p-fluorobenzoic acid (FBA) and p-methylbenzoic acid (MBA), are used as post-assembly molecules to effectively fill the voids between the [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz) molecules to form a denser HSL, which facilitates passivation of the perovskite buried interface. In addition, post-assembled BAs with different dipole moments can effectively adjust the work function of Me-4PACz HSL, facilitating the transport and extraction of charge carriers. Consequently, the PSCs based on Me-4PACz/FBA HSL realize a champion PCE of 25.58%. Moreover, the unencapsulated devices maintain 82% and 94% of the PCE after 800 h of the outdoor storage (RH≈60%) and 2000 h in glove box, respectively. This post-assembly technique enhances both the PCE and stability of the device, blazing a simple and effective pathway for further development of PSCs.