Comparative DFT Studies of Optoelectronic Properties of MTPA Derivatives

Accurate prediction of optical and electronic properties of methyl triphenyl amine (MTPA) and its derivatives was investigated as these properties are essential for designing efficient electron donor material for organic solar cell applications. Specifically, we have investigated ten different density functionals used in the Density Functional Theory (DFT) and Time Dependent DFT (TD-DFT) calculations to determine the best functional for predicting the HOMO, LUMO, Egap and UV-Vis absorption spectra of MTPA and its derivatives accurately. The ten density functionals namely, B3LYP, B3PW91, HSEH1PBE, MPW1PW91, CAMB3LYP, B97XD, BPV86, PBE, TPSS, and HCTH were investigated with the 6-31g+(d,p) basis set. MTPA and six MTPA derivatives in dichloromethane solvent were studied. Results show that among the ten functionals, HSEH1PBE is the best functional in predicting HOMO, LUMO and Egap of MTPA and MTPA derivatives with an overall MAE of 0.43 eV for all three properties mentioned. MAE for HOMO, LUMO and Egap of MTPA derivatives tend to decrease as the functional group attached becomes more electron-withdrawing. This trend was observed to be opposite for TD-DFT excitation calculations used for UV-Vis absorption spectra. Absorption wavelength MAE increases as the functional group attached to MTPA becomes more electron-withdrawing. The best functional in predicting absorption spectra of MTPA and MTPA derivatives is CAMB3LYP with MAE of 26nm.