Abstract:

The synthesis, characterization, and photovoltaic performance of two new organic dyes, hexapropyltruxeneamino-rhodanine-3-acetic acid(MXD8) and hexapropyltruxeneamino-3,4-ethylenedioxythiophene rhodanine-3-acetic acid(MXD9), were reported. The two dyes contain truxene-based triarylamine as electron donor and a rhodanine-3-acetic acid as electron acceptor. It is found that the two dyes exhibit broad absorption and high molar absorption coefficients. The ground and the excited state levels of the two dyes were determined by using the cyclic voltammetry and the optical absorption spectroscopy. The results show the HOMO and LUMO levels of two dyes are suitable for dye-sensitized solar cells. The dyes were applied into nanocrystalline TiO2 dye sensitized solar cells through standard operations. Under simulated AM 1.5 irradiation(100×10-3 W/cm2), MXD8 sensitized cell afforded a short-circuit photocurrent density(JSC) of 5.76×10-3 A/cm2, an open circuit voltage(VOC) of 614 mV, and a fill factor(FF) of 0.66, corresponding to an overall conversion efficiency(η) of 2.33%. In contrast, though 3,4-ethylenedioxythiophene(EDOT) unit was introduced as the π-bridge, MXD9 sensitized cell gave a lower efficiency of 1.72%. A significantly larger extent of charge recombination between the injection electron and I2 and/or I-3 acceptor species was found for MXD9 dyes than MXD8 dyes based on the electrochemical impedance spectroscopy measurements, consequently, leading to a lower efficiency. These results suggest that the charge recombination may be correlated to the increased polarizability of the larger truxene-based triarylamine dyes. From our findings, we propose that the functionalized-truxene is a promising donor unit for the future development of organic sensitizers.

Key words: dye-sensitized solar cell, organic dyes, power conversion efficiency, truxene