D-A-π-A organic dyes for dye-sensitized solar cells: effect of π-bridge length between two acceptors on photovoltaic properties

We report synthesis, photophysical and photovoltaic properties of organic dyes with D-A-π-A backbone having 1,3,4-oxadiazole moiety as an auxiliary acceptor, triphenylamine as donor with varying π-bridges and acceptors. The effect of increased distance between the auxiliary acceptor and main acceptor on their photovoltaic properties is studied with the help of optical and electrochemical spectroscopy, quantum chemical calculations, current-voltage (I-V) measurements, incident photon-to-current conversion efficiency (IPCE) and electrochemical impedance spectroscopy (EIS). The length of the π-bridge of the studied dyes has significant effect on the photophysical and photovoltaic properties. Dye OD3 with the longest π-bridge has superior performance in dye-sensitized solar cells compared to other dyes.