High open circuit voltage organic photovoltaic cells based on oligothiophene derivatives

Abstract
For the purpose of developing organic photovoltaic devices with good performance characteristics, The authors have fabricated two cells using 5-vinyl-2,2′:5′,2″:5″,2‴-quarterthiophene (V4T), 5-vinyl-2′:5′,2″:5″,2‴:5‴,2″″-quinquethiophene (V5T) and 3,4,9,10-perylenetertracarboxylic dianhydride (PTCDA). The indium tin oxide (ITO)/V4T/PTCDA/Al cell has an open circuit voltage (Voc) of 2.07V and a photoelectric conversion efficiency of 2.32%. The ITO/V5T/PTCDA/Al cell has an Voc of 1.87V and a photoelectric conversion efficiency of 2.67%. The two cells have higher Voc (1.87–2.07V). It is possible that intermolecular hydrogen bonding between –CHCH2 group of VnT with carboxylic dianhydride of PTCDA contributes to the enhancement by promoting forward interfacial electron transfer and eliminating the subconducting band trap sites.