In situ Blending For Co‐Deposition of Electron Transport and Perovskite Layers Enables Over 24% Efficiency Stable Conventional Solar Cells

Abstract Simplifying the manufacturing processes of multilayered high‐performance perovskite solar cells (PSCs) is yet of vital importance for their cost‐effective production. Herein, an in situ blending strategy is presented for co‐deposition of electron transport layer (ETL) and perovskite absorber by incorporating (3‐(7‐butyl‐1,3,6,8‐tetraoxo‐3,6,7,8‐tetrahydrobenzo‐ [lmn][3,8]phenanthrolin‐2(1H)‐yl)propyl)phosphonic acid (NDP) into the perovskite precursor solutions. The phosphonic acid‐like anchoring group coupled with its large molecular size drives the migration of NDP toward indium tin oxide (ITO) surface to form a distinct ETL during perovskite film forming. This strategy circumvents the critical wetting issue and simultaneously improves the interfacial charge collection efficiencies. Consequently, n‐i‐p PSCs based on in situ blended NDP achieve a champion power conversion efficiency (PCE) of 24.01%, which is one of the highest values for PSCs using organic ETLs. This performance is notably higher than that of ETL‐free (21.19%) and independently spin‐coated (21.42%) counterparts. More encouragingly, the in situ blending strategy dramatically enhances the device stability under harsh conditions by retaining over 90% of initial efficiencies after 250 h in 100 °C or 65% humidity storage. Moreover, this strategy is universally adaptable to various perovskite compositions, device architectures, and electron transport materials (ETMs), showing great potential for applications in diverse optoelectronic devices.