Improving the performance and stability of perovskite solar cells via surface passivation of phthalimide N-alkylammonium iodides

Surface defects induce non-radiative charge recombination and reduce the photovoltaic performance of perovskite solar cells (PSCs). To realize highly efficient and stable PSCs, surface passivation is an effective strategy to reduce defects in mixed halide perovskite films. Organic iodides have emerged as valuable candidates for perovskite surface passivation owing to their facile preparation, optimal lattice matching with perovskites, and robust defect passivation capability. Here, a novel phthalimide N-alkylammonium iodide (PAE-I) is introduced as a passivating agent for the defects on the surface of FAPbI(3) perovskite films. The incorporated PAE-I layer effectively passivates interface traps and reduces non-radiative recombination, improving carrier extraction and transfer. As a result, the power conversion efficiency (PCE) of PSCs increases from 19.76% to 21.30%. Furthermore, the PAE-I-passivated PSCs without encapsulation exhibit excellent long-term stability, retaining 80% of the initial efficiency after 2400 hours under an ambient atmosphere. This work provides deep insights into the reduction of non-radiative recombination and the enhancement of device performance through the application of phthalimide as a superior and promising passivator.