Flexible Organic Photovoltaics with Star‐Shaped Nonfullerene Acceptors End Capped with Indene Malononitrile and Barbiturate Derivatives

Abstract

The design and synthesis of three star‐shaped nonfullerene (NFA) acceptors, TPA‐2T‐INCN, TPA‐2T‐BAB, and TPA‐T‐INCN, based on a triphenylamine (TPA) core and linked through π‐conjugated thiophene (T) spacers to different terminal units (3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene) malononitrile, INCN, and 1,3‐dimethylbarbituric acid, BAB), are reported. These materials are blended with the widely used poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) donor polymer and tested in flexible organic photovoltaics (OPVs). The NFAs capped with the strong electron‐withdrawing INCN unit perform best in OPVs. Both P3HT:TPA‐T‐INCN and P3HT:TPA‐2T‐INCN blends also show the highest photoluminescence quenching efficiency (95.8% and 92.6%, respectively). Surprisingly, when reducing the number of T spacers from 2 to 1, the solubility of the NFAs in o‐dichlorobenzene increases, leading to easier processing during the OPV fabrication and better surface morphology. This explains the best performance of TPA‐T‐INCN‐based blends in OPVs, with a champion power conversion efficiency of 1.13%.

Cyano-capped molecules: versatile organic materials

“…Furthermore, 8a has been reported to promote an efficient charge extraction process while limiting charge recombination at the interface. 43 In contrast to odd-membered oligothiophenes 7 (Fig. 3), Zhou et al developed tetrathiophene (4T) semiconductors 9ad with two FIC acceptors (Fig.…”

“…Furthermore, 8a has been reported to promote an efficient charge extraction process while limiting charge recombination at the interface. 43…”