Interfacial electron transfer in whole functional dye-sensitized solar cell

This project is related to the following Fields, Subjects and Techniques:

Since Dye-sensitized solar cell (DSSC) was developed by Gratzel and coworkers, it has become a promising and low cost alternative to conventional silicon semiconductor solar cell. DSSC is mainly composed of dye-sensitized semiconductor electrode, redox electrolyte and counter electrode. Once dye molecules absorb light, the excited dye injects electron to semiconductor, at the same time, oxidized dye cation is reduced by redox electrolyte which competes with the recombination of injected electron and dye cation (see figure). Because interfacial electron transfer kinetics (competition among electron injection, recombination and regeneration) plays an important role in controlling the efficiency of DSSC, a better understanding at those processes is needed for further improving DSSC performance.

So far, by the use of the ultrafast spectroscopy technique, the electron injection has been shown by our group to take place with multiexponential kinetics from less than 100 femtoseconds to tens of picoseconds. The electron recombination between injected electron and dye cation has a nonexponential behavior and spans from microseconds to milliseconds. However, most of the present work is based on dye-sensitized semiconductor films (working electrode), instead of the whole functional solar cell. In the whole solar cell the working efficiency of the DSSC is not only influenced by electron injection and recombination processes between dye and semiconductor, but also other factors, such as dye regeneration by electrolyte, ionic transport, electrolyte composition, and conduction band trap filling. Using femtosecond time-resolved spectroscopy combined with nanosecond time-resolved spectroscopy we are investigating how these factors are influencing interfacial electron transfer dynamics in whole solar cells.