Journal
CHEMISTRY OF MATERIALS
Volume 23, Issue 19, Pages 4394-4401Publisher
AMER CHEMICAL SOC
DOI: 10.1021/cm202226j
Keywords
dye sensitizers; solar cells; benzotriazole; open-circuit photovoltage; charge recombination
Funding
- National Basic Research Program of China [2011CB933302]
- National Natural Science Foundation of China [20971025, 90922004, 50903020]
- Shanghai nongovernmental international cooperation program [10530705300]
- Shanghai Leading Academic Discipline Project [B108]
- Oriental Scholarship
- Fundamental Research Funds for the Central Universities [WK1013002]
- Jiangsu Major Program [BY2010147]
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Two novel benzotriazole-containing organic dyes based on D-A-pi-A configuration, WS-5 with octyl group and WS-8 with methyl group, have been designed and synthesized for use in dye-sensitized solar cells (DSSCs). Compared with the traditional D-pi-A sensitizers, the benzotriazole unit as an additional acceptor has several merits: (i) essentially facilitating the electron transfer from the donor to the acceptor/anchor; (ii) conveniently tailoring the solar cell performance with a facile structural modification on 2-position in the benzotriazole unit; and (iii) the nitrogen-containing heterocyclic group of benzotriazole being expected to improve the open-circuit photovoltage. The analysis of controlled intensity modulated photovoltage spectroscopy reveals that the replacement of methyl with octyl group enhances electron lifetime by 4-fold and retards charge recombination rate constant by 4-fold. The two dye-loaded TiO(2) films possess almost the same conduction band position under the same condition, as revealed by the charge densities at open-circuit against open-circuit photovoltage. Therefore, the significant enhancement of open-circuit photovoltage from methyl to octyl group is attributed to the suppressed charge recombination. Under simulated AM1.5G solar light (100 mW cm(-2)), the DSSC based on WS-5 produces a short-circuit photocurrent of 13.18 mA cm(-2), an open-circuit photovoltage of 0.78 V, a fill factor of 0.78, corresponding to a power conversion efficiency of 8.02%.
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