In-depth interfacial engineering for efficient indoor organic photovoltaics

Alternative approaches to interlayer optimization are urgently required to realize efficient indoor organic photovoltaics owing to the substantially different indoor light conditions compared to outdoor light conditions (1 sun). In this work, an in-depth study was undertaken on electron-collecting interlayers (ECIs) comprising poly-(ethyleneimine)-ethoxylated (PEIE) modification, zinc oxide (ZnO) nanoparticles (NPs), or a combination of the ZnO NPs and PEIE modification. Morphological, optical, and electrochemical properties of the ECIs were investigated using atomic force microscopy (AFM), ultraviolet-visible (UV–vis) spectrometry, and a Kelvin probe, respectively. Inverted poly(3-hexylthiophene-2,5-diyl):indene-C60 bisadduct (P3HT:ICBA)-OPVs with the ECIs were fabricated. While poor photovoltaic behavior was observed for OPVs with the ZnO NPs owing to the relatively large work function of the ECI under LED light in the absence of UV light, outstanding indoor performance was achieved by OPVs with PEIE modification as the PEIE contributed to work function reduction of the ECI. In particular, OPVs with the ZnO NPs/PEIE ECI yielded the highest efficiencies of up to 14.1 ± 0.3% under 1000-lx LED lamp. In this study, we have fabricated OPVs with various electron-collecting interlayers (ECIs) and studied electrical and optical mechanisms under indoor light conditions. The ECI Bilayer improves device performance by minimizing the leakage current of the device under indoor light conditions and effectively controlling the work function of the ITO substrate. [Display omitted] •3 types of electron-collecting interlayers were introduced to indoor OPVs PEIE, ZnO NPs, and ZnO NPs/PEIE.•P3HT:ICBA-based OPVs containing the electron-collecting interlayers were fabricated.•Relatively high work function of ZnO NPs under LED light possibly induced energy level mismatch.•OPV devices with ZnO NP/PEIE yielded an efficiency of up to 14.1% under 1000 lx LED illumination.