A Nonfullerene Semitransparent Tandem Organic Solar Cell with 10.5% Power Conversion Efficiency

Semitransparent organic solar cells have great potential for building integrated photovoltaics and power-generating windows owing to their advantages of light weight, mechanical flexibility, and color tunability. However, the performance of previous semitransparent organic solar cells have been limited by their relatively weak optical absorptions. In this paper, an efficient nonfullerene semitransparent tandem organic solar cell that exhibits a broad absorption from 300 to 1000 nm is reported. The rear subcell is based on a narrow-bandgap nonfullerene acceptor named IEICS-4F that exhibits a strong crystallinity and high electron mobility. As a result, the IEICS-4F-based single-junction opaque and semitransparent organic solar cells yield high efficiencies of 10.3% and 7.5%, respectively. To further enhance light harvesting of the single-junction semitransparent organic solar cells while maintaining a decent transmittance, a semitransparent tandem organic solar cell is fabricated by incorporating a medium-bandgap P3TEA:FTTB-PDI₄ blend as the front subcell. A high efficiency of 10.5% is recorded with an average transmittance of 20%.