Inhibiting interfacial transport loss for efficient organic nonfullerene solar cells and photodetectors

Nonfullerene organic solar cells (OSCs) and photodetectors have received tremendous interest due to their rapidly progressed power conversion efficiency (PCE) and wide range photoresponse to near-infrared region, respectively. Further optimization of the interfacial transport layer is one of the key factors toward enhanced performance. Herein, we reported a general multi-component electron transport layer (ETL) strategy to achieve better energy level alignments and interfacial contact for both OSCs and photodetectors. The binary polymer:molecule blend based ETL can overcome low crystallinity and self-aggregation issue in neat polymer and molecule ETL, respectively. The mixed blend provides a more tunable platform to optimize the interfacial morphology and creates more efficient charge-transporting pathways. We showcase that the PNDIT-F3N:PDINN binary ETL exhibits its strength in a series of nonfullerene OSCs with enhanced fill factor and current density, achieving a champion PCE approaching 19%. Additionally, self-powered organic photodetectors with lower dark current and high detectivity were achieved with the same binary ETL strategy. Detailed morphology and device characterizations reveal that the binary ETL modulates the interfacial interface to deliver a more favorable energy level alignment, facilitating carrier extraction and transport. We believe these findings could provide insight into the design of ETL with sufficient interfacial tunability for organic optoelectronic devices.