New Semiconducting Polymer Based on Benzo[1,2-b:4,5-b']diselenophene Donor and Diketopyrrolopyrrole/Isoindigo Acceptor Unit: Synthesis, Characterization and Photovoltaics

Two new D-A type polymers PBDSe-DPP and PBDSe-ID were synthesized to explore new ideal semiconducting polymers, by conjugating acceptor unit diketopyrrolopyrrole/isoindigo to a donor unit benzo[1,2-b:4,5-b']diselenophene, which is designed by substituting the sulfur atom with a selenium atom in the benzo[1,2-b: 4,5-b']dithiophene. The thermal, optical, electrochemical, photoelectric and photovoltaic properties of the two polymers were studied systematically. Relatively high open circuit voltage (0.7 and 0.75 V) and fill factor (>65%) were demonstrated for both polymers. Huge increase (by 64% and 120%) of the short circuit current density was achieved for both polymer based devices by using additive compared to the corresponding reference without additive, resulting in decent power conversion efficiency of 3.7% and 2.5% respectively with only simple optimizing consideration. We believe this class of BDSe polymer possesses a good potential to be alternatives of active material for photovoltaic applications.