Quantum chemical investigation of modified coumarin-based organic efficient sensitizers for optoelectronic applications

One of the most major features in the improvement of dye-sensitized solar cells (DSSCs) is the survey and plan of high-efficiency and low-cost dyes. In this paper, a new series of metal-free coumarin-based (NKX-2311) dye molecules, namely (D1–D4) are investigated for use in DSSC applications. The dye molecules contain three parts, electron-donor (D) connected by the π-conjugated linker as a spacer and electron-acceptor (A)/anchoring group. Molecular structure, electronic absorption spectra and photovoltaic (PV) parameters of the D1–D4 dyes have been performed by using density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches are employed. The effects of chemical modification on the spectra and PV properties of the coumarin-modified organic dyes have been revealed. The performance of three functionals (B3LYP, CAM-B3LYP and ωB97XD) has been evaluated to get an experimental absorption wavelength of NKX-2311. From the functionals, B3LYP method was better matched with the absorption wavelength of NKX-2311. Therefore, D1–D4 dye molecules excited state calculations of the absorption spectra have been investigated by using B3LYP functional with 6-31G(d) basis set. The results show that D1, D3 dyes are smaller energy gap and absorption spectra are systematically red-shifts. The theoretical results have a display that the lowest occupied molecular orbitals (LUMOs) and highest occupied molecular orbitals (HOMOs) of the D1–D4 dyes can be confirming positive response on the electron injection and dye regeneration process. The NLO property of the D1–D4 dyes can be derived as polarizability and first-order hyperpolarizability. The calculated values of D1 and D3 dyes are the best applicants for NLO performance. The conclusion of this study will deliver a useful reference to the future proposal and beneficial to get DSSCs with superior power conversion efficiency (PCE).