A Partial Metal Coordination Strategy toward High-Performance and Cost-Effective Electron Transporting Layer for Organic Solar Cells

Additives are frequently employed in the active layer of organic solar cells (OSCs) to fine-tune morphology and improve overall device performance. The use of additive in electron transporting layer (ETL) has garnered less attention. In this study, poly(2-vinyl pyridine) (P2VP) based cost-effective ETLs are developed for OSCs. Addition of CoCl2 to the P2VP affords ETLs with enhanced conductivity and optimized work function. OSCs employing this ETL demonstrate prolonged carrier lifetime, suppressed charge recombination, and achieve higher power conversion efficiencies (PCEc) than the commonly used ETLs such as PFNBr and Phen-NaDPO. The cost of the P2VP-Co is merely one-twentieth of that associated with Phen-NaDPO or PFNBr. Mechanism studies and density functional theory (DFT) calculations reveal that the partial metal salt coordination of P2VP leaves free pyridine rings for dipole interactions with the Ag electrode, and provides higher electrostatic potentials and larger dipole moments compared to the polymer alone, thereby increasing conductivity. The polymer and metal salt additive strategy demonstrates its effectiveness in boosting device performance, offering valuable possibility for designing novel electronic materials and expanding the applications of widely available polymers. Partial coordination of poly(2-vinyl pyridine) (P2VP) leads to an augmented electrostatic potential and heightened dipole moments, thereby fostering elevated conductivity and controlled energy levels. Simultaneously, the uncoordinated pyridine rings facilitate interaction and contact with the Ag electrode.image (c) 2024 WILEY-VCH GmbH