2. Computational Details
The analytical solution to the problems related to structural modifications and modeling of photoinjection in organic dyes is a cumbersome task. Thanks to the development of different commercial codes and upgradation of computational infrastructures in recent past, the numerical solution to such problems with high reliability, precision and reproducibility are now possible. This work was carried out using LCAO (linear combination of atomic orbitals) based approach implemented in DFT code ADF (Amsterdam Density Functional) version 2018 which performs DFT, time dependent DFT (TD-DFT) [51] and Density-Functional based tight binding (DFTB) calculations [52] by computationally employing formulism of Kohn-Sham theory in fast and efficient way [53].
In order to investigate the effects of structural modification of carbazole-donor based organic dye on photoinjection, three dyes, named here as D1, D2 and D3 , shown in figure 2, were used as reference [23]. The length of the π-spacer of carbazole-donor based organic dye with oligothiophene π-spacer having carboxylic acid as acceptor was increased by adding thiophene units.