Low-bandgap alternating fluorene copolymer/methanofullerene heterojunctions in efficient near-infrared polymer solar cells

Efficient near-IR polymer solar cells based on the low-bandgap alternating fluorene copolymer APFO-Green 5 (shown in the figure) exhibit a photo-response up to 800 nm. The copolymer performs well in combination with the common electron acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), reaching a power-conversion efficiency of 2.2% with a lower PCBM content in the active layer than previous devices based on low-bandgap polymers.