Modelling of Charge Transport in Organic Devices

Abstract

When we talk about flexible electronic devices, the type of interface plays a key role. While designing a device at the molecular level and optimization of its performance depends upon charge injection and its transport through the interface. So in our work, we have studied the interface between organic molecule and conductor, using density functional theory (DFT), and Non equilibrium green function (NEGF) approach. For computing the coupling integral, we used Koopman’s theorem and the electronic coupling for holes (or electrons) resulting from the mixing of the frontier orbital’s of the two nearest donor (or acceptor) molecules with the orbital’s of the bridging acceptor (donor) molecule. For open systems, the density matrix is calculated using NEGF, while for closed or periodic systems it is calculated by using diagonals from the Kohn-Sham Hamiltonian. Coupling between the molecule and electrodes plays an important role in electronic transport because it shifts and expands the molecular levels dramatically and changes the HOMO-LUMO gap in different manners due to their distinct electronic structures.