modeling and design of a single donor/acceptor molecule photodetector based on orbital resonance using the dft+negf method

In this study, we present a photodetector based on molecular donor/acceptor (d/a) interactions utilizing orbital resonance (or). the device operates by detecting light through interactions between donor and acceptor molecules, resulting in electronic or optical changes. the unique properties of the designed photodetector make it a valuable tool in various fields, including molecular electronics. initially, molecule optimization and band structure calculations were performed using the density functional theory (dft) approach to determine the energy and states of the bipartite molecule. subsequently, the system's hamiltonian was calculated based on these results. the non-equilibrium green's function (negf) formalism was then employed to model the photodetector using the optimized molecule. we utilized the self-consistent field (scf) method and optical energy coefficients for modeling. key photodetector properties such as photocurrent, quantum efficiency (qe), and responsivity (r) were calculated and compared using photons with energies of 1 ev. next, the current-voltage curve was extracted with and without light exposure. results indicated negative differential resistance at bias voltages of 2.425 v, 7.54 v, -1.36 v and -6.34 v depending on the input light frequency. the device exhibited a qe=10.2% and an r=0.34 (a/w). additionally, we modeled the charging effect in the photodetector. two parameters, quantum and electrostatic capacitance, were proposed to model this effect. furthermore, the current-voltage curve was displayed considering the charging effect. the designed device also demonstrated the ability to detect and absorb waves at different frequencies.