Cost-effective organic solar cells consisting of homogeneously passivated metal oxides
Organic solar cells (OSCs) have achieved power conversion efficiencies (PCEs) exceeding 20% in laboratory-scale devices, yet challenges persist in developing cost-effective charge-transporting materials (CTMs) that ensure high performance and long-term stability. Conventional organic CTMs such as PEDOT:PSS and PDINN suffer from thermal instability due to molecular diffusion and phase segregation. Solution-processed metal oxides (MOs) offer excellent stability and cost-effectiveness but are plagued by surface defects, particularly hydroxyl groups, which act as recombination centers and photocatalytic sites, degrading device interfaces. Here, we develop an organic-inorganic hybrid strategy to homogeneously passivate solution-processible semiconducting MOs. By first synthesizing MOs rich in surface hydroxyl groups and then introducing organic molecules, we achieve chemically homogeneous passivation that mitigates surface defects. This approach enables favorable interfacial energy level alignment, enhanced charge extraction, and tunable surface energy. Employing these passivated MOs as electron transport layers (ZnO) and hole transport layers (NiOx), we achieve a champion PCE of 20.22% for all-MO CTM-based OSCs, the highest reported to date. Scalability is demonstrated via ambient blade-coating, yielding 18.33% PCE for large-area cells (1.44 cm2) and 16.03% for modules (20.05 cm2), with material costs estimated at only 4% of organic counterparts. Furthermore, devices exhibit outstanding stability, retaining over 80% of initial PCE after 1300 h of maximum power point tracking and over 1000 h of thermal annealing at 85°C. This work establishes a new benchmark for cost-effective, high-performance organic photovoltaics.