Enhancement in Nonlinear Optical Response of Oligothiophenes by Induction of Polarons

Abstract

In this study, the electronic and nonlinear optical properties of neutral ((nTh) and polaronic states (nTh*) of oligothiophenes are studied. Electronic properties are evaluated through HOMO–LUMO gap, ionization potential (IP), and electronic affinity (EA). The results of global reactivity descriptors also indicate the stability of nTh*. The linear and nonlinear optical properties are evaluated through the polarizability and static and dynamic hyperpolarizabilities. The polaronic states of these polymers show high hyperpolarizability (βo) up to 2.7 × 104 au as compared to neutral counterparts. This remarkable increase is mainly due to low transition energies arising from the induction of polaron. The NLO response of polaron-based oligothiophenes are much better than their neutral counterparts. Furthermore, the frequency dependent calculations for polaronic state of oligothiophenes (nTh*) are also performed at commonly used laser frequencies of 532 and 1064 nm. The results of frequency dependent calculations reveal that the values of dynamic hyperpolarizability are more pronounced than static hyperpolarizability. Time-dependent calculations show enough transparency of polaronic state of nTh* in the UV region, which reveals that the materials show good NLO response and could be used in the field of optoelectronics.