Synthesis and organic photovoltaic (OPV) properties of triphenylamine derivatives based on a hexafluorocyclopentene “core”

A series of new “D-A-D” chromophores containing hexafluorocyclopentene thiophene as an acceptor and a triphenylamine unit as a donor, called TP-G1, TP-G2, TPB-G1 and TPB-G2, were designed and synthesized. Heterojunction organic photovoltaic (OPV) cells containing these chromophores were fabricated, and device 1, with the structure of ITO/PEDOT:PSS/TP-G1:P3HT/LiF/Al, displayed an open-circuit voltage (Voc), short-circuit current (Jsc) and power-conversion efficiency (η) of 0.74 V, 1.178 mA/cm2 and 0.22%, respectively. The triphenylamine group could effectively induce the open-ring isomer to close because the 4- and 4′- positions of the benzene rings were substituted by an electron-donating group and the value of the quantum yields of the closed-ring isomers increased. As a result, the closed-ring isomer facilitated intramolecular π-electron delocalization and exhibited a broad absorption band ranging from 200 to 850 nm. Due to the fluorine substitution of hexafluorocylopentene at the molecular center and the hole-transport characteristics of the triphenylamine moiety on the periphery, our chromophores showed obvious dual semiconductor properties, i.e., n- and p-type, which demonstrated a potential application for OPV devices.