A Unified Quantum Mechanical Framework for Modelling Charge Transport in Organic Semiconductor Devices Fabricated from Nigerian Biopolymers

Organic semiconductor devices fabricated from sustainable biopolymer sources represent a frontier of green electronics research with significant implications for Nigeria's transition toward locally manufactured electronic components. Charge transport in these disordered materials occurs through hopping between localised states and band-like transport in ordered regions, necessitating a unified quantum mechanical framework that transcends the limitations of purely classical drift-diffusion models. This study develops a unified quantum mechanical framework for modelling charge transport in organic semiconductor devices based on cassava starch-derived biopolymers and cellulose acetate films processed at the University of Nigeria, Nsukka. The framework combines Marcus-Levich-Jortner theory for hopping transport with coherent transport contributions described by the non-equilibrium Green's function formalism, unified through a polaron quantum master equation that bridges the weak and strong coupling limits. Parameterisation of the framework uses molecular dynamics trajectories of the biopolymer chain conformations combined with time-dependent DFT electronic coupling calculations. The model's predictions for charge carrier mobility as a function of temperature and electric field are validated against temperature-dependent space-charge-limited current measurements performed on biopolymer thin film diodes. Results indicate that the unified framework reduces mobility prediction error from 45 percent (classical model) to 12 percent across the 200 to 350 K temperature range. Keywords: charge transport, organic semiconductor, biopolymer, quantum master equation, Nigeria