Tailoring Polypyrrole and Polyaniline Polymers by Introducing Side Groups for Sensing and Photovoltaic Applications: A DFT Study
Shivangi Garg, Neetu Goel
Abstract
The study presents evidence gathered from density functional-based computational approach to assess the suitability of polypyrrole (PPy) and polyaniline (PAni) chains functionalized with different electron-donating (EDG) and -withdrawing (EWG) groups as sensing and photovoltaic devices. The results indicate that introducing strong EWG (such as CN and NO2) in polymer backbone chains makes these conjugated organic polymers, a potential donor material in polymer-based solar cells. The photovoltaic efficiency has been expressed in terms of parameters like exciton binding energy (Eb), offset between LUMO levels (ΔELUMO), and open circuit voltage (VOC) and is measured with reference to commonly used fullerene-based acceptor material. The calculated values of VOC imply the applicability of CN and NO2 functionalized polymer derivatives in photovoltaic devices. Apart from photon absorption in the visible spectrum, the frontier orbitals of CN and NO2 substituted derivatives are suitably aligned with the frontier orbitals of the acceptor to facilitate charge transfer between the two. A significant reduction in Egap and enhancement in absorption wavelength (λmax) by attaching NO2 and NH2–NO2 infers their suitability for sensing applications. Therefore, NO2 and NH2–NO2 functionalized polymer derivatives opted for the sensitivity and selectivity toward different analytes (such as NO, NO2, and N2O), and all the optimizations were performed at the theory level of B3LYP/6-31G(d). Interaction between selected polymer derivatives and analytes has been interpreted in terms of interaction energy, frontier orbital analysis, charge transfer, and optical absorption spectra.