Electronic and Optical Properties of N-doped BBL Polymer

Since their discovery, conducting polymers have been widely studied over the last few years in many optoelectronic applications. Applying redox chemistry, the intrinsic conductivity of the polymers could be altered by adding/removing an electron to make the polymer as an n-type/p-type material, respectively. The charge transport in electronic devices depends on the performance of both the p-type and n-type materials. P-doped polymers have been extensively studied over n-doped polymers due to lack of stable n-doped polymers. The need of the hour is to study n-type polymer to improve the performance of organic electronic devices. Here we study n-doped poly(benzobisimidazobenzophenanthroline) (BBL) using ground-state and time-dependent (TD) density functional theory (DFT). High electron mobilities (~0.1 cm² V^–1 s⁻¹), high structural and thermo-oxidative stability make BBL as an ideal n-doped polymer. To understand the electronic structure and optical spectroscopy of n-doped BBL, a thorough theoretical study is carried out. Formation of polaron and bipolaron due to the reduction of BBL is analyzed by ωB97XD functionals DFT with the 6-31+G(d) basis set. UV visible absorption spectra from TDDFT calculations show the transition from polaron/bipolaron to the conduction band.