High Open‐Circuit Voltage (1.197 V) in Large‐Area (1 cm²) Inverted Perovskite Solar Cell via Interface Planarization and Highly Polar Self‐Assembled Monolayer

Abstract The efficiency loss caused by area scaling is one of the key factors hindering the industrial development of perovskite solar cells. The energy loss and contact issues in the buried interface are the main reasons. Here, a new self‐assembled monolayer (SAM), Ph‐4PACz, with a large dipole moment (2.32 D) is obtained . It is found that Ph‐4PACz with high polarity can improve the band alignment and minimize the energy loss , resulting in an open‐circuit voltage ( V oc ) as high as 1.2 V for 1.55 eV perovskite. However, when applied to large‐area devices, the fill factor (FF) still suffered from significant attenuation. Therefore, alumina nanoparticles (Al 2 O 3 ‐NPs) are introduced to the interface between Ph‐4PACz and rough FTO substrate to further improve the flatness , resulting in a conformal perovskite film with almost no voids in the buried interface, thus promoting low exciton binding energy, fast hot‐carrier extraction and low non‐radiative recombination. The final devices achieved a small‐area power conversion efficiency (PCE) of 25.60% and a large‐area (1 cm 2 ) PCE of 24.61% (certified at 24.48%), which represents one of the highest PCE for single device ≥ 1 cm 2 area. Additionally, mini‐modules and stability testing are also carried out to demonstrate the feasibility of commercialization.