The solution-processable electron transport layer (ETL) is essential for the electron transport and extraction of inverted perovskite solar cells (PSCs). A new naphthalene diimide based copolymer with phosphite ester pendants (PFNDI) is developed as an ETL in inverted PSCs. The naphthalene diimide backbone and the phosphite ester pendants endow PFNDI a good electron transport property and a strong binding force on perovskite. By introducing PFNDI on the perovskite interface, we succeed in improving surface morphologies of perovskite film, reducing the trap density and facilitating electron transport properties. The PFNDI-based devices exhibit an optimal power conversion efficiency of 18.25% (with the V_OC = 1.068 V, J_SC = 22.53 mA cm⁻² and FF = 75.85%) and fine long-term stabilities. The un-encapsulated PFNDI-based devices maintain 80% of their initial performance after storage for more than 500 h at 20 °C in air with a relative humidity of 25% and 75% of their initial efficiency after continuously heating for about 300 h. Our work demonstrated that NDI-based polymers with proper pendant groups can be the ideal n-type organic materials for high-performance PSCs.

可溶液处理的电子传输层（ETL）对于反向钙钛矿太阳能电池（PSC）的电子传输和提取至关重要。开发了一种新的基于亚磷酸二酯侧基的萘二酰亚胺基共聚物（PFNDI）作为反向PSC中的ETL。萘二酰亚胺主链和亚磷酸酯侧基赋予PFNDI良好的电子传输性能，并且对钙钛矿具有很强的结合力。通过在钙钛矿界面上引入PFNDI，我们成功地改善了钙钛矿膜的表面形貌，降低了陷阱密度并促进了电子传输性能。基于PFNDI的器件表现出18.25％的最佳功率转换效率（V _OC  = 1.068 V，J _SC  = 22.53 mA cm ^-2且FF = 75.85％）和良好的长期稳定性。未封装的基于PFNDI的器件在20°C的空气中存储超过500小时后，其相对湿度为25％，在连续加热约300小时后，其初始效率为其初始效率的75％，该器件的初始性能保持了其80％的初始性能。我们的工作表明，具有适当侧基的NDI基聚合物可以成为高性能PSC的理想n型有机材料。