Efficiency enhancement of P3HT:PCBM polymer solar cells using oligomers DH4T as the third component

We assembled a ternary blend bulk heterojunction polymer solar cell (PSCs) containing P3HT (donor) and PC₆₁BM (acceptor) incorporated with a dihexyl-quaterthiophene (DH4T) small molecule oligomer as a third component. By optimizing the contents of DH4T, we increased the power conversion efficiency of ternary P3HT:DH4T:PC₆₁BM PSCs to 4.17% from 3.44% of binary P3HT:PC₆₁BM PSCs under AM 1.5 G of 100 mW/cm² intensity. The major improvement is from the increase of the short circuit current and fill factor that is due to the increased light absorption at short wavelength, the balanced charge carrier transportation and the enhanced hole evacuation by a DH4T-enriched layer at the anode interface. In this work, we demonstrate that the efficiency of the PSCs can be enhanced by using low-bandgap conjugated polymer and its oligomer as donors and fullerene derivatives as acceptors.