Bulk-Heterojunction Organic Solar Cells Based on Benzobisthiadiazole Semiconducting Polymers

Benzobisthiadiazole (BBT)-containing donor-acceptor polymers were investigated as semiconductors in bulk-heterojunction organic solar cells. Taking advantage of the polarity change of the BBT-based copolymers in terms of comonomer structures, they were examined as both p-type and n-type semiconductors. In the case of n-type semiconductors, fullerene-free organic solar cells were fabricated. A power conversion efficiency (PCE) of 0.02% was achieved when fluorenyl hexa-peri-hexabenzocoronene (FHBC) was employed as a p-type semiconductor. The limited performance might be due to the strong intermolecular pi-pi stacking of BBT-based copolymers, resulting in the poor miscibility between the donor molecule and acceptor polymer.