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Natural Chlorophyll-Related Porphyrins and Chlorins for Dye-Sensitized Solar Cells
Research Center for Organic Electronics, Graduate School of Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan
Energy Technology Research Institute and Research Center for Photovoltaic Technologies, National Institute of Advanced Industrial Science and Technology (AIST), Higashi 1-1-1, Tsukuba, Ibaraki 305-8568, Japan
* Author to whom correspondence should be addressed.
Received: 13 March 2012; in revised form: 5 April 2012 / Accepted: 6 April 2012 / Published: 13 April 2012
Abstract: Natural-chlorophyll-related porphyrins, including (2H, Zn, Cu)-protoporphyrin IX (Por-1) and Zn-mesoporphyrin IX (Por-2), and chlorins, including chlorin e6 (Chl-1), chlorin e4 (Chl-2), and rhodin G7 (Chl-3), have been used in dye-sensitized solar cells (DSSCs). For porphyrin sensitizers that have vinyl groups at the β-positions, zinc coordinated Por-1 gives the highest solar-energy-to-electricity conversion efficiency (h) of up to 2.9%. Replacing the vinyl groups of ZnPor-1 with ethyl groups increases the open-circuit voltage (Voc) from 0.61 V to 0.66 V, but decreases the short-circuit current (Jsc) from 7.0 mA·cm−2 to 6.1 mA·cm−2 and the value of h to 2.8%. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations suggest that the higher Jsc values of Zn-based porphyrin sensitizers result from the favorable electron injection from the LUMO at higher energy levels. In the case of the chlorin sensitizers, the number of carboxyl protons has a large effect on the photovoltaic performance. Chl-2 with two carboxyl protons gives much higher values of Jsc, Voc, and h than does Chl-1 with three carboxyl protons. Replacing the protons of Chl-1 with sodium ions can substantially improve the photovoltaic performance of Chl-1-based solar cells. Furthermore, the sodium salt of Chl-3 with an aldehyde group at the C7 position shows poorer photovoltaic performance than does the sodium salt of Chl-1 with methyl groups at the C7 position. This is due to the low light-harvesting capability of Chl-3.
Keywords: porphyrin; chlorin; dye-sensitized solar cell; photosynthesis; organic photovoltaics
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Wang, X.-F.; Kitao, O. Natural Chlorophyll-Related Porphyrins and Chlorins for Dye-Sensitized Solar Cells. Molecules 2012, 17, 4484-4497.
Wang X-F, Kitao O. Natural Chlorophyll-Related Porphyrins and Chlorins for Dye-Sensitized Solar Cells. Molecules. 2012; 17(4):4484-4497.
Wang, Xiao-Feng; Kitao, Osamu. 2012. "Natural Chlorophyll-Related Porphyrins and Chlorins for Dye-Sensitized Solar Cells." Molecules 17, no. 4: 4484-4497.