Highly efficient and stable organic solar cells with SnO2 electron transport layer enabled by UV-curing acrylate oligomers

The interfaces between the inorganic metal oxide and organic photoactive layer are of outmost importance for efficiency and stability in organic solar cells (OSCs). Tin oxide (SnO2) is one of the promising candidates for the electron transport layer (ETL) in high-performance inverted OSCs. When a solution-processed SnO2 ETL is employed, however, the presence of interfacial defects and suboptimal interfacial contact can lower the power conversion efficiency (PCE) and operational stability of OSCs. Herein, highly efficient and stable inverted OSCs by modification of the SnO2 surface with ultraviolet (UV)-curable acrylate oligomers (SAR and OCS) are demonstrated. The highest PCEs of 16.6% and 17.0% are achieved in PM6:Y6-BO OSCs with the SAR and OCS, respectively, outperforming a device with a bare SnO2 ETL (PCE 13.8%). The remarkable enhancement of PCEs is attributed to the optimized interfacial contact, leading to mitigated surface defects. More strikingly, improved light-soaking and thermal stability strongly correlated with the interfacial defects are demonstrated for OSCs based on SnO2/UV cross-linked resins compared to OSCs utilizing bare SnO2. We believe that UV cross-linking oligomers will play a key role as interfacial modifiers in the future fabrication of large-area and flexible OSCs with high efficiency and stability.