A new small molecule acceptor based on indaceno[2,1-b:6,5-b'] dithiophene and thiophene-fused ending group for fullerene-free organic solar cells

Abstract

A new small molecule acceptor of IDTCN with indaceno[2,1-b:6,5-b’]dithiophene as electron-donating core and CPTCN (2-(6-oxo-5,6-dihydro-4H-cyclopenta[c]thiophen-4-lidene)malononitrile) as electron-withdrawing end-capping group was synthesized and investigated in organic solar cells. The IDTCN shows strong and broad absorption with a high extinction coefficient and appropriate energy levels matching with wide bandgap donor polymer. The best device based on PBT1-EH:IDTCN exhibits an open circuit voltage (Voc) of 0.93 V, a short circuit current (Jsc) of 13.31 mA/cm2, a FF of 0.702, achieving a PCE of 8.69%.