A high-light-harvesting-efficiency of NKX-2593 and NKX-2883 Coumarin dyes in a local electric field: Can a local electric field enhance dye sensitizer solar cells efficiently?

The electronic structures and optical absorption spectra of organic dye sensitizers NKX-2593 and NKX-2883 were studied by using density functional theory (DFT), and the vertical excitation energies were calculated within the framework of the time-dependent DFT (TD-DFT) approach both in the gas phase and in ethanol solution. The solvent effects provide changes in both the geometries and the absorption spectra. Electric fields influence any process or transition that involves charge transfer, as a result of Stark effect. Stark spectroscopy is a general expression describing the study of spectral changes in electric fields, and it has been verified to be a broadly functional approach for characterizing the change in dipole moment and polarizability for electronic transitions. The results of this work show that field application, parallel to the dipole moment, can be very effective to increase DSSC efficiency. Our results open the possibility of computationally screening the various predictions on the electronic structure, optical response and in consequence their influences on the efficiency, thus paving the way to an effective molecular engineering of further enhanced sensitizers for solar cell applications.

► Field application in proper direction can lead to a change in the absorption spectrum. ► PBE1PBE and MPW1PW91 are suitable for calculating maximum absorption spectra of dyes. ► NBO analysis provides a direct insight into the π-conjugation strength of dyes.