Dye sensitized solar cells (DSSCs) are commonly regarded as a promising next generation solar cell technology1 because they have good performance at ~13% and can be made relatively inexpensively without intensive purification and fabrication steps. However, the liquid electrolyte of conventional DSSCs is prone to leakage and evaporation, which hinders DSSC applications, durability, and thermal stability. Novel polymer electrolyte DSSCs can overcome the shortcomings and can enhance the cell I-V behavior. Recent experimental studies have demonstrated that polymer electrolytes are good alternatives to liquid electrolytes in DSSCs2-4.
There have been relatively few studies that combine experimental and computational/theoretical approaches to better understand DSSC processes and optimize DSSC performance. Currently, there is a need for a better understanding of how polymer electrolyte chemistry affects the cell performance. Accurate first-principles models can provide this better understanding. By properly accounting for the physical and electrochemical processes occurring inside the cells, the models can elucidate competing effects within DSSC components, can identify factors that affect the overall cell performance, and can guide experimental work in designing cell materials.
Continuing our previous work5, 6 on the mathematical modeling of liquid-electrolyte and polymer-electrolyte DSSCs, in this work we theoretically and experimentally investigate the effects of polymer-electrolyte chemistry on the performance of polymer-electrolyte DSSCs. Using steady-state and transient models we predict current-voltage behavior and model the frequency response of DSSCs to simulate electrochemical impedance spectroscopy (EIS). The frequency response is performed to investigate the electronic and ionic processes in DSSCs. Using the macroscopic models, we conduct parametric sensitivity studies to identify key parameters that limit cell efficiency and recognize how the parameters affect cell behavior. Furthermore, to gain a complete understanding of the photochemical processes inside the DSSCs, the first-principles macroscopic modeling is coupled with experiments involving initiated chemical vapor deposition to synthesize and incorporate the polymer electrolytes within the mesoporous TiO2 photoanode. Using the experimental data and the model, we will elucidate the effects of polymer chemistry on the cell performance, and determine how and why the photochemical processes inside such solar cells are altered by the polymer electrolytes. Parameter estimation using the macroscopic model indicates that a shift in the conduction band of TiO2 and a suppression of the back electron transfer at the dye-TiO2-electrolyte interface are induced by the chemical groups of the polymers.
1. O. Mari, O. Kei, S. Ai, T. Hideyuki, H. Nozomu, E. Akira, T. Hiromitsu, K. Momoji and M. Akira, Japanese Journal of Applied Physics, 2010, 49, 04DP10.
2. A. F. Nogueira, J. R. Durrant and M. A. De Paoli, Advanced Materials, 2001, 13, 826-830.
3. P. Wang, S. M. Zakeeruddin, J. E. Moser, M. K. Nazeeruddin, T. Sekiguchi and M. Gratzel, Nat Mater, 2003, 2, 402-407.
4. S. Nejati and K. K. S. Lau, Nano Letters, 2010, 11, 419-423.
5. M. Bavarian, S. Nejati, K. K. S. Lau, D. Lee and M. Soroush, Industrial & Engineering Chemistry Research, 2014, 53(13), 5234-5247.
6. Y. Y. Smolin, S. Nejati, M. Bavarian, D. Lee, K. K. S. Lau and M. Soroush, Journal of Power Sources, 2015, 274, 156-164.
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