Triphenylamine-substituted methanofullerene derivatives for enhanced open-circuit voltages and efficiencies in polymer solar cells

A new class of triphenylamine substituted methanofullerene derivatives, bis(4ʹ-(diphenylamino)biphenyl-4-yl)methanofullerene (1) and the bisadduct (2), were synthesized. The incident photon to current efficiency (IPCE) studies revealed that the diphenylamino components have contribution to the photocurrent that expands the light harvesting window around 400 nm. When being blended with poly (3-hexylthiophene) (P3HT) to fabricate the solar cell, the device of P3HT:1 (1:0.7) shows high open circuit voltage (Voc) of 0.69 V under the illumination of AM 1.5, 100 mW/cm2 with high power conversion efficiency (PCE) of 3.16%, which is about 0.1 V higher than that of the corresponding [6,6]-phenyl C61 butyric acid methyl ester (PCBM) devices. This indicates that the arylamine substituents on 1 have played some special roles on the high Voc performance. Similar effects are also observed for 2. The device of P3HT:2 (1:1) shows even higher Voc of 0.87 V with the PCE of 1.83%. These results indicate that 1 and 2 are alternative high performance acceptors.