Linear correlation between DSSC efficiency, intramolecular charge transfer characteristics, and NLO properties – DFT approach

Abstract

Abstract The trends in the dye-sensitizer solar cells (DSSCs) efficiencies of 4 N, N-dimethylaniline-based polyene sensitizers, NKX-2553, NKX-2554, NKX-2600, and NKX-2569 have been correlated with the trends in intramolecular charge transfer characteristics as revealed by the trends in non-linear optical (NLO) properties. Both an electron-donor and π-linkers play a vital role in the performance of the sensitizer/dye in the DSSCs as well as in NLO properties. Optimized geometries showed that the cyanoacrylic acid unit is planar with the π-bridge, including a methine, a thiophene and two methine units, and a donor unit, confirming an extensive an electron transfer. Natural Bond Orbital (NBO) analysis for metal-free organic sensitizer has been shown that the electron transfer occurs from an electron donor (D) to electron acceptor (A) units. Bond length change (BLA) values demonstrate a good relationship with ascertained estimation of second-order hyperpolarizability. The singlet–triplet investigation demonstrates that the sensitizer having a required estimation of the singlet–triplet energy gap, and it is a good contender for the DSSCs application. Frontier molecular orbital (FMO) analysis showed that both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) have electron localization support the electron transfer characters. These results give the direction for optimizing the metal free organic dyes as efficient sensitizers/dyes in Dye-Sensitized Solar Cells (DSSCs) and NLO applications.