Inorganic/Organic Electron Transport Interface Engineering for Planar and Fiber-Shaped Organic Solar Cells

Using an interfacial modifier (IM) agent to overcomeinterfacialproblems of zinc oxide (ZnO), which is commonly used as an electrontransport layer (ETL), is an effective interfacial engineering strategythat can be used to improve the performance and stability of optoelectronicdevices, such as inverted organic solar cells (iOSCs).In this work, a conjugated polymer electrolyte (CPE) is employed asan IM agent to modify the surface morphology of ZnO ETL-based iOSC devices. Compared to a pristine ZnO ETL, the CPE-modifiedZnO (CPE/ZnO) ETL is more hydrophobic with a smooth surface inducedby an interfacial dipole, resulting in better energy alignment tothe LUMO of the photoactive layer. The power conversion efficiency(PCE) of poly(3-hexylthiophene) (P3HT) and phenyl-C-60-butyricacid methyl ester (PCBM) blend-based planar iOSCswith a CPE/ZnO ETL increases from 3.8% to 4.2% and from 1.8% to 2.2%for bottom and top transparent devices, respectively. The CPE/ZnOETL is further employed to fabricate a fiber-shaped iOSC (FS-iOSC), which is a promising wearable optoelectronicdevice. In FS-iOSCs fabricated by a dip-coating methodwith a CPE/ZnO ETL, the PCE improves to 1.02%, which is a near 2-foldimprovement over devices using a pristine ZnO ETL. Additionally, ourconcept has also been successfully applied to inverted polymer light-emittingdiodes (iPLED) with planar and fiber-shaped configurations.These results suggest that the surface modification of metal oxideETLs (e.g., ZnO) with organic interfacial modifiers (e.g., CPE) isa simple but effective approach to fabricating planar and fiber-shapedoptoelectronic devices with high performance.