Novel Quinoxaline-Based Organic Dye with Heteroleptic Dual Electron Donor for Dye-Sensitized Solar Cells

A novel quinoxaline-based organic dye with heteroleptic dual electron donors (phenoxazine and carbazole) on each side of a quinoxaline was designed, and its electronic and optical properties were investigated theoretically for applications to dye-sensitized solar cells (DSSCs). To understand the factors influencing the photovoltaic efficiency, density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations of these dyes were performed. The absorption spectrum of the dyes showed different forms because of the different energy levels of the molecular orbital (MO) of each dye and the intramolecular charge-transfer (ICT) characteristics. The asymmetric organic dye with the heteroleptic dual donor showed competitive conversion efficiency, greater red-shift, broader absorption spectra, and higher molar extinction coefficient compared to dyes with homoleptic dual donors. These results indicate that adding a withdrawing unit and heteroleptic donor produces good photovoltaic properties for DSSCs.