Poly(3-hexylthiophene):indene-C60 bisadduct morphology improvement by the use of polyvinylcarbazole as additive

Bis-indene fullerene (ICBA) is a highly symmetric molecule that tends to diffuse and aggregate into larger clusters, resulting in a huge horizontal phase separation when the master solvent vaporizes, in addition to a significant drop in power conversion efficiency (PCE). We found that Poly(3-hexylthiophene) (P3HT): indene-C60 bisadduct (ICBA) blended with a high-molecular-weight polyvinylcarbazole (PVK) film could effectively prevent the clustering of ICBA crystalline molecules, thereby improving the phase separation. Furthermore, PVK dispersed the ICBA:P3HT active layer in a more uniform manner, increasing open circuit voltage (Voc) and reducing photocurrent loss. As a result, the PCE of the device can be improved from 2.2% to 4.5%.