Highly Semitransparent Indoor Nonfullerene Organic Solar Cells Based on Benzodithiophene-Bridged Porphyrin Dimers

Two acceptor-donor-acceptor-based porphyrin dimers, C8TEBDT-2P and C8TBDT-2P, are presented as donors for high-performance semitransparent indoor organic photovoltaics. Both compounds vary in that benzodithiophene (BDT) bridged the two porphyrins at the meso-carbon directly for the latter with a less planar structure, and via ethynylene for the former with a more planar structure. As a result, the C8TEBDT-2P exhibits a more red-shifted absorption profile from 400 to 800 nm than the C8TBDT-2P from 400 to 700 nm due to stronger π-conjugation. Using indaceno-dithiophene-indene-dimalononitrile (IDIC) as a nonfullerene acceptor, the blend film C8TEBDT-2P:IDIC shows a promising power conversion efficiency (PCE) of 12.3% under indoor (300 lux light-emitting diode) and a PCE of 7.46% under one sun illuminations. The improved efficiency of the device C8TEBDT-2P: IDIC is mainly due to highly ordered surface morphology, that leads in efficient charge separation, faster charge transport, and less charge recombination. Furthermore, the photopic properties indicate that both devices have good transparency and chromaticity, with an average visible transmittance value of 70% for C8TEBDT-2P:IDIC and 73% for C8TBDT-2P:IDIC. This study enriches the pool of porphyrin donors for highly semi-transparent indoor nonfullerene organic solar.