Acene-modified triphenylamine dyes for dye-sensitized solar cells: a computational study

Area of Science:

• Materials Science
• Computational Chemistry
• Renewable Energy

Background:

• Organic sensitizers are crucial for dye-sensitized solar cells (DSSCs).
• Triphenylamine (TPA) derivatives with acene modifications offer tunable electronic and optical properties.
• Metal-free dyes are desirable for sustainable and cost-effective solar cell technologies.

Purpose of the Study:

• To investigate a series of metal-free acene-modified triphenylamine dyes (TPA-AC1 to TPA-AC5) as organic sensitizers for DSSCs.
• To elucidate the impact of varying acene unit sizes on the dyes' spectral and electrochemical characteristics.
• To computationally assess the interfacial electronic structures between the dyes and TiO(2) nanoparticles.

Main Methods:

• Density Functional Theory (DFT), DFTB, and Time-Dependent DFT (TDDFT) calculations were employed.
• Simulations of dye/(TiO(2))(46) anatase nanoparticle systems were performed.
• Analysis of key parameters including electron injection enthalpy, light-harvesting efficiency, and semiconductor band edge shifts.

Main Results:

• Increasing acene size (TPA-AC1 to TPA-AC5) led to broader, red-shifted absorption and fluorescence spectra.
• Oscillator strength and electron injection properties decreased with larger acene units.
• Molecular orbital contributions showed increased localization on acene units as size increased.

Conclusions:

• TPA-AC3, featuring an anthracene moiety, exhibited a favorable balance of electron injection, light-harvesting efficiency, and semiconductor band alignment.
• TPA-AC3 is identified as a promising metal-free dye candidate for DSSCs, aligning with experimental findings.
• This study provides insights for designing novel TPA-based organic dyes to enhance DSSC performance.