Dual-side interfacial passivation of FAPbI₃ perovskite film by Naphthylmethylammonium iodide for highly efficient and stable perovskite solar cells

Interfacial passivation has been considered as an effective strategy to improve the performance of perovskite solar cells (PSCs) by modifying defect trap states between perovskite and charge transport layers. Here, we apply Naphthylmethylammonium Iodide (NMAI) salt to passivate the double-side interfaces from the perovskite/electron transport layer (ETL) and perovskite/hole transport layer (HTL). It demonstrates that using NMAI to suppress the interface defects from perovskite film can effectively decrease non-radiative recombination, extend the carrier recombination lifetime (from 4 to 113 ns), and boost PSCs device performance. Additionally, the judicious control of the interaction between perovskite and NMAI molecules can further optimize the homogenous morphology and crystallinity of the perovskite absorber layer. The double-side NMAI passivated device achieved a decent 22.97 % power conversion efficiency (PCE) with 1.11 V of open-circuit voltage (V_OC), 80.35 % fill factor (FF) and short-circuit current (J_SC) of 25.77 mA cm⁻², compared to the control device (19.56 % PCE in conjunction with an V_OC of 1.01 V, FF of 79.67 %, and J_SC of 24.37 mA cm⁻²). Moreover, the unencapsulated devices with double-side NMAI passivation layers maintain 73 % of initial PCE after 432 h, at room temperature, under a nitrogen atmosphere, and in dark conditions. This study proposes a facile and effective method to passivate the perovskite/ETL and perovskite/HTL interfaces via NMAI spin-coating process.