High-performance polymer photovoltaics based on rationally designed fullerene acceptors

A novel C70 fullerene derivative ICBM was rationally designed and synthesized by [4+2] cyclic addition reaction between an indene derivative (methyl 4-(1H-inden-3-yl)butanoate) and C70. The absorption and photoluminescence of the mixed films of ICBM with different polymer donor materials were characterized. The electrochemical reduction behavior of ICBM in the range of 0 to −2.5 V was investigated by the cyclic voltammetry method, and the result shows that the lowest unoccupied molecular orbital (LUMO) level of ICBM is 0.07 eV higher than that of PC70BM. The photovoltaic devices based on poly (3-hexylthiophene) (P3HT) and a low band gap polymer (PTB7) as donors, with ICBM as an acceptor gave power conversion efficiencies of 5.00% and 6.67%, respectively. The result demonstrates that this novel C70 fullerene derivative is a much better acceptor for wide-band gap as well as low-band gap donor polymers in the BHJ polymer photovoltaics.