Organic small molecule modifies the perovskite layer to prepare efficient and stable inverted perovskite solar cells

The perovskite layer is the core component of perovskite solar cells (PSCs), and the quality of the perovskite film critically impacts the performance of PSCs. Interfacial contact optimization, defect passivation, and energy level alignment regulation are effective approaches to fabricate high-performance PSCs. Herein, an organic small molecule, 5-bromopyridine-2,3-dicarboxylic acid (BPDCA), is doped into a perovskite precursor solution to serve as the photosensitive layer of PSCs. Density functional theory (DFT) simulations and systematic characterizations confirm that BPDCA can optimize the crystallization quality of the perovskite and passivate defects in the perovskite film through the N atom on the pyridine ring and the O atom on the carboxyl group. Meanwhile, BPDCA doping optimizes the energy level matching, promotes the extraction and transport of charges, and enhances the open-circuit voltage (V_oc). The PSCs fabricated with BPDCA doping achieve a power conversion efficiency (PCE) of 20.75%, with a V_oc of 1.13 V. The unencapsulated device maintains more than 90% of the initial PCE after 1000 h of exposed storage in an air atmosphere. This work offers a straightforward and effective strategy for obtaining efficient and stable PSCs through functionalized perovskites.