Electrochemical polymerization effects of triphenylamine-based dye on TiO2 photoelectrodes in dye-sensitized solar cells

This study reports on the photophysical properties of a triphenylamine (TPA)-based indoline dye (TPAR) and its polymer-type dye (PTPAR) via electropolymerization, and their application in dye-sensitized solar cells (DSSCs). In the TPAR dye, the TPA group and rhodanine-3-acetic acid act as the basic electron donor and the electron acceptor, respectively. The TPA unit in TPAR is readily employed to perform electropolymerization due to its aniline derivative-like molecular structure. The resulting polymer dye (PTPAR) exhibits a network structure of π-conjugation polymer chains that produce a significant blue shift in the absorption spectrum. This phenomenon stabilizes the intramolecular charge transfer from donor units to electron acceptors under light irradiation. The incident photon-to-current conversion efficiency (IPCE) of TPAR-sensitized DSSC has a higher value than PTPAR dye, exceeding 70% in the range of 470–510 nm. The lower IPCE of PTPAR-sensitized devices are ascribed to the blue shift of PTPAR dye. TPAR-based DSSC are more efficient (4.57%) than PTPAR-based DSSCs (3.04%). The efficiency of gel-type DSSCs is significantly lower ∼47% than that of liquid-type DSSCs for both dyes.