Spectroscopic and HLCT Analysis on 4,7-Di(2-Thienyl)-2,1,3-Benzothiadiazole and Its Di-Substituted Derivatives for Development of Potent Hole Transport Material: DFT Approach |
| B. Felcia Merlin, R. Amrutha
Department of Physics, KCG College of Technology, Chennai-600097, India |
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| In the present study, the doping effect of the di-substitution of F, Cl, CH3, OCH3, OH, NO2 to the reference donor-acceptor molecule 4,7-di-(2-thienyl)-2,1,3-benzothiadiazole (DTBT) has been reported by quantum chemical calculations in hybrid local charge transfer (S0→S1) state exciton process. The variation in molecular geometry confirms the charge transfer from the reference donor-acceptor unit to the substituted groups, except for the CH3 substitution. The UV-Visible absorption, fluorescence emission, and Raman spectral characterization of the investigated systems validate the incidence of charge transfer. In frontier molecular orbital analysis, the decrease in the energy gap value of DTBT molecule after the addition of substituents indicates the intramolecular charge transfer from the donor-acceptor unit to the substituents, except for DTBT:CH3. It also reveals higher charge carrier mobility in the investigated systems. The ionization potential, electron affinity, and re-organization energy analyses confirm that DTBT:OH molecular system causes the energy barriers to be reduced, displaying higher hole and electron transportability compared with the parent DTBT molecule and other substituents. The natural bond orbital analysis provides evidence that the DTBT:OCH3, DTBT:OH, and DTBT:NO2 molecular systems can be useful in the design of nonlinear optical materials. The natural population analysis confirms that the electron charge carrier mobility from the donor-acceptor unit to the substituted group increases upon the doping of halogen atoms. The calculated first-order hyperpolarizability value reveals that DTBT:NO2 molecule has a higher value compared to that of all other investigated systems. Hence, the present study will be useful in the design of novel hole transport materials. |
DOI:10.12693/APhysPolA.141.445 topics: 4, 7-di-(2-thienyl)-2, 1, 3-benzothiadiazole, Raman, NLO, hole transport materials |