Synthesis Of Asymmetrical Triarylamine Organic Photosensitizer Based On Truxene And Application In DSSCs

The development and utilization of solar energy is of great significance with energy and environmental issues become increasingly prominent. Dye-sensitized solar cells(DSSCs)have attracted much attention because of their potential to achieve efficient conversion of sunlight into electricity at low costs and their high efficiency.A new generation of dye-sensitized solar cells(DSSCs) is based on a combination of D–π–A organic dyes in conjunction with cobalt-based redox mediators. Therefore, we developed a series of triarylamine organic dyes(M36-M39) toward cobalt electrolytes and investigated their photophysical, electrochemical properties, and their photovoltaic performance based on cobalt electrolytes. The main conclusions are as follows:1. Traditionally, organic dyes were obtained through the Suzuki reaction between a borate complex of electron donor and π-conjugate bridge. However, this method is not suitable for this type of dyes. In this work, a new synthetic method was used. Namely, the truxene amino was cross-coupled with π-conjugate bridge fist, and then another electron donor was introduced. Furthermore, the yield is higher and the products are easy to purify.2. M36 and M37 display an obvious absorption between 540-560 nm with high molar extinction coefficients. The results indicate that introduction of truxene as the electron donors of the dyes broaden the absorption band and enhance the light absorption.3. The introduction of different terminal donors has a great impact on the energy level of the dyes, thus affecting the regeneration efficiency of the dyes and photovoltaic performance of the cells, which suggests that we can effectively improve the photoelectric conversion efficiency of the triarylamine organic dyes through molecular design.4. Recombination kinetics of cobalt(III) complexes at titania/dye interface are also studied using electrochemical impedance spectroscopy and controlled intensity modulated photovoltage spectroscopy measurements. Our results show that, for M36 sensitized DSCs, a Marcus inverted region can be reached for the charge recombination kinetics behavior of cobalt(III) species. While that for DSCs based on M37 just lies in the Marcus normal region.The results can be attributed to differences in the retarding charge recombination ability of the self-assembled dye layer. Benefiting from a Marcus inverted region behavior, the M36 dye exhibits a good compatibility with the [Co(phen)3]3+/2+ redox couples, achieving a high overall power conversion efficiency(PCE) of 9.58% under full sun illumination.We also designed and synthesized two other triarylamine organic dyes M38 and M39.However, Lack of time precludes the investigation of the photophysical/electrochemical properties and the photovoltaic performance for both dyes.