The function of Chalcogenophene in the Cyclomatelated Ring of the Cycloruthenated Dyes applied in Dye-Sensitized Solar Cell

The-Duy Nguyen; Yen-Po Lan; Chun-Guey Wu

doi:10.1021/acs.inorgchem.1c01293

The function of Chalcogenophene in the Cyclomatelated Ring of the Cycloruthenated Dyes applied in Dye-Sensitized Solar Cell

Inorg Chem. 2021 Aug 2;60(15):11328-11337. doi: 10.1021/acs.inorgchem.1c01293. Epub 2021 Jul 19.

Authors

The-Duy Nguyen¹, Yen-Po Lan¹, Chun-Guey Wu¹

Affiliation

¹ Research Center for New Generation Light Driven Photovoltaic Modules and Department of Chemistry, National Central University, Jhong-Li, 32001 Taiwan, Republic of China.

PMID: 34278784
DOI: 10.1021/acs.inorgchem.1c01293

Abstract

Three thiocyanate-free cycloruthenated complexes, DUY24-O, DUY24, and DUY24-Se containing furan, thiophene, and selenophene, respectively, as a part of the cycloruthenated ring, were designed to reveal the function of the chalcogen atom on the physicochemical and photovoltaic performance of the cycloruthenated sensitizers applied in dye-sensitized solar cells (DSCs). The three sensitizers have a similar molecular size; therefore, the effect of molecular dimensions on their photovoltaic performance can be negligible. NMR data, electron-donating resonance effects, optical properties, and the energy levels of the frontier orbitals reveal that the physical/photovoltaic properties of the three sensitizers were affected significantly by the chalcogen atom on the cyclometalated chalcogenophene ring. The λ_max (both in ethanol and adsorbed on TiO₂), frontier orbital level, and dye loading of thiophene- and selenophene-containing dyes are very close. Nevertheless, DUY24-Se has a higher molar absorption coefficient compared to DUY24; therefore, the DSC based on DUY24-Se has higher efficiency (8.4% under AM1.5 G one-sun and 26% under T5-light at ca. 6000 lux) than that sensitized with the DUY24 dye. These efficiencies are also higher than those (7.9 and 21.6%, respectively) of the cell dyed with N719, fabricated using the same conditions. The better performance of the device sensitized with DUY24-Se compared to DUY24-based cells suggests that selenophene is as good as (or even better than) thiophene to be a part of the cyclometalated ring for thiocyanate-free cycloruthenated sensitizers applied in DSCs. Furan-containing DUY24-O has much worse photovoltaic performance compared to the other two dyes. This is not only because DUY24-O has the shortest λ_max, the lowest molar absorption coefficient, and the highest HOMO level but also the lowest dye loading (because of the strong interaction between the oxygen in furan and TiO₂, the array of DUY24-O occupies more surface when adsorbed on TiO₂) and the fastest charge recombination. The physicochemical and photovoltaic properties as well as the adsorption behavior of the dye on the TiO₂ anode for the cycloruthenated sensitizers affected significantly by the chalcogen atom of the chalcogenophene on the cyclometalated ring provide a new strategy to design high-efficiency NCS-free cyclometalated sensitizers for DSCs.