Enriching the electronic populations of D-π-A type ON-OFF solar switches with sp2 hybridization: A TD-DFT possibility to create pull-push effect

Abstract

The ability of specific molecular acceptors in photovoltaic devices is determined by their structure and chemical composition. Multiscale computations are important to protect investigation design; hence, efforts and money could be saved. Using Density Functional Theory (DFT), the effect of sp2 hybridized nitrogen substitutions (Ns) at the specific positions of a solar cell dye, 2,2′-((4-heptyl-4,9,9-trihexyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b']dithiophene-2,7-diyl)bis(methanylylidene)bis(3-oxo-2,3-dihydro-1H-indene-1-yl-2-ylidene)dimalononitrile (IDIC), is explored. The N-incorporated dyes (IDIC1-IDIC5) were optimized at their ground energy minima at the B3LYP level of DFT with 6-31G+(d,p) basis sets. From these optimized geometries, their UV–visible analysis was executed at the DFT functional of CAM-B3LYP/6-31G+(d,p) selected as a result of benchmarking their λmax values with experimental values of IDIC. The computed value was found to be 528 nm which was very near to its experimental value (540 nm). Interestingly, for all the new dyes, λmax had blue-shifted values of (502–513 nm) for IDIC1, IDIC2 and IDIC5 and red-shifted values (557–779 nm) for IDIC3 and IDIC4 as compared to IDIC. The highest second-order Non-Linear Optical (NLO) response of 1054 e.s.u was noted for IDIC4 and IDIC5 which had the lowest energy gaps. It was found that incorporating Ns has significantly decreased the energy gap of electron rearrangement.