Indoloindole-based small molecule bulk heterojunction small molecule solar cells

An acceptor-donor-acceptor (A-D-A) conjugated small molecule, DHII-EH-TR, was designed, synthesized, and its solar cell performance studied. The DHII-EH-TR molecule with its extended fused aromatic core had a narrow bandgap and displayed red-shifted absorption. To investigate its photovoltaic properties and device application, small molecule-based organic photovoltaics (SMOPVs) were fabricated having the conventional structure of ITO/PEDOT:PSS/DHII-EH-TR:PC70BM/ZnO NPs/Al (PEDOT:PSS, poly (3,4-ethylenedioxythiophene):polystyrene sulfonic acid; ZnO NPs, ZnO nanoparticles). Solar cells made with a blend of 1,8-diiodooctane with ZnO NPs generated the highest performance with a power conversion efficiency (PCE) of 3.60%. Charge dynamics and transport, microscopic thin film analysis, and morphology were studied to explain the performance of SMOPVs made with DHII-EH-TR.