Synthesis of seleno[3,4-c]pyrrole-4,6-dione-based polymers for polymer solar cells

Novel π-conjugated polymers PSePDBDT1 and PSePDBDT2 containing seleno[3,4-c]pyrrole-4,6-dione and benzo[1,2-b:4,5-b′]dithiophene units were synthesized, and their thermal, optical and photovoltaic properties were compared with those of the corresponding thiophene-based polymer, PTPDBDT2, containing sulfur instead of selenium. PSePDBDT2 exhibited higher thermal stability and a narrower bandgap than PTPDBDT2. Using PSePDBDT2 or PTPDBDT2 as an electron donor and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as an electron acceptor, inverted-type bulk heterojunction photovoltaic devices with the configuration ITO/TiOx/PSePDBDT2 or PTPDBDT2:PC61BM (1:2, w/w)/PEDOT:PSS/Au (ITO = indium tin oxide, TiOx = titanium oxide, PEDOT:PSS = poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonic acid)) were fabricated. The preliminary power conversion efficiencies of the devices containing PSePDBDT2 and PTPDBDT2 were 0.28% and 1.54%, respectively, under simulated AM1.5 solar irradiation (77.8 mW/cm2).