Abstract
The photoelectrical properties of two dyes—ethyl red and carminic acid—as sensitizers of dye-sensitized solar cells were investigated in experiments herein described. In order to reveal the reason for the difference between the photoelectrical properties of the two dyes, the ground state and excited state properties of the dyes before and after adsorbed on TiO2 were calculated via density functional theory (DFT) and time-dependent DFT (TDDFT). The key parameters including the light harvesting efficiency (LHE), the driving force of electron injection () and dye regeneration (), the total dipole moment (), the conduction band of edge of the semiconductor (), and the excited state lifetime (τ) were investigated, which are closely related to the short-circuit current density () and open circuit voltage (). It was found that the experimental carminic acid has a larger and , which are interpreted by a larger amount of dye adsorbed on a TiO2 photoanode and a larger , excited state lifetime (τ), , and . At the same time, chemical reactivity parameters illustrate that the lower chemical hardness (h) and higher electron accepting power (ω+) of carminic acid have an influence on the short-circuit current density. Therefore, carminic acid shows excellent photoelectric conversion efficiency in comparison with ethyl red.
Highlights
Solar energy, as a clean and renewable energy, has many advantages including inexhaustibility, no pollution, and large-scale applications
dye-sensitized solar cell (DSSC) sensitized with the two dyes in the visible light region, we found that the DSSCs sensitized with ethyl red were too weak in the visible light region; the incident photo-to-current conversion efficiency (IPCE) spectrum of the DSSC sensitized with carminic acid is mainly discussed in this paper
Through the analysis of the light harvesting efficiency (LHE) of the dye, the injection efficiency of the electrons in the excited state (Φinj ), and the regeneration efficiency of the dye, the improved ηreg of carminic acid is caused by the fact that larger ∆Gregen is favorable to the greater short-circuit current density, which is in agreement with the experimental value
Summary
As a clean and renewable energy, has many advantages including inexhaustibility, no pollution, and large-scale applications. Li and co-workers [29] investigated three natural dyes (Forsythia suspensa, Herba Violae, and corn leaf) as potential sensitizers, and the highest PCE was 0.96%, with open circuit voltage of 0.66 V, a short-circuit current density of 1.97 mAcm−2 , and a fill factor of 0.74 among the three DSSCs. In recent years, quantum chemical methods have become a feasible means to reveal the relationship between structures and properties of dye molecules, which provide a reliable theoretical basis for the rapid screening of highly efficient dye molecules [30,31].
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