Interface Modification of Tin Oxide Electron‐Transport Layer for the Efficiency and Stability Enhancement of Organic Solar Cells

Abstract A small molecular phenanthroline derivative Phen‐NaDPO (3‐[6‐(diphenylphosphinyl)‐2‐naphthalenyl]‐1,10‐Phenanthroline) to modify tin oxide (SnO 2 ) electron‐transport layer (ETL) in organic solar cells is employed. Quantum chemistry calculations and experimental results show that Phen‐NaDPO can interact with SnO 2 , thereby effectively passivating the surface defects, reducing the work function and improving the electrical conductivity of SnO 2 , leading to more efficient electron extraction and transport in the organic solar cells (OSCs). Moreover, upon the Phen‐NaDPO modification, the decreased surface energy of SnO 2 ETL accounts for enhanced exciton dissociation and charge transport, due to the more ordered molecular organizations of the active layers. Consequently, the inverted OSCs involving Phen‐NaDPO/SnO 2 ETLs exhibit an enhanced power conversion efficiency of 17.06% (PM6:Y6) and 18.31% (PM6:L8‐BO), which is the highest efficiency for SnO 2 ETL‐based binary solar cells to date. Furthermore, the devices based on Phen‐NaDPO/SnO 2 ETL show better device stability (storage stability, photostability and humid stability), with T 80 exceeding 200 h encapsulated under light irradiation and 400 h without encapsulation in high‐humidity ambient condition. These results demonstrate that the modification of SnO 2 using wide‐band highly stable conjugated small molecules is very promising for simultaneously improve the efficiencies and device stability of OSCs.