Highly Efficient Nonfullerene Organic Photovoltaic Devices with 10% Power Conversion Efficiency Enabled by a Fine‐Tuned and Solution‐Processed Hole‐Transporting Layer

Solution‐processable hole‐transporting materials are demonstrated to improve the performance of nonfullerene‐based organic photovoltaic devices in an inverted structure. A vanadium oxide (VOX) precursor, used as a sol–gel, is mixed with commercial poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to form a well‐dispersed VOX:PEDOT:PSS solution. The work function and molecular distribution of the VOX:PEDOT:PSS thin film are examined by ultraviolet photoelectron spectroscopy (UPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), respectively. Unlike conventional PEDOT:PSS, VOX:PEDOT:PSS not only is compatible with highly hydrophobic photoactive layers but also aligns well with the highest occupied molecular orbital (HOMO) level of the polymer donor, reaching a power conversion efficiency of 10% (≈100% boost) and achieving an excellent device stability. A simple and effective method of fine‐tuning the energy level of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) is demonstrated. The as‐prepared hole‐transporting material aligns well with the highest occupied molecular orbital level of the electron donor in nonfullerene‐based organic photovoltaic (OPV) devices in inverted architecture, reaching a power conversion efficiency of 10%, which would benefit the future commercialization of highly efficient OPV devices.