FDTD modelling and simulation of organic photo detector using photonic crystals

Abstract

In this work, modelling and simulation of Organic Photo Detector (OPD) is carried out using Finite difference time domain (FDTD) method. By interposing photonic crystals into the OPD, the electric field intensity is significantly enhanced compared to conventional photo detectors. The optical effects such as power absorption is observed by interposing water soluble conjugate polymer layer such as poly(9,9-bis(3’-(N,N-dimethylaminopropyl)-2,7-fluorene)-alt- 2,7-(9,9 dioctyl fluorene)] (PFN) as interlayer into the OPD device structure. Propitious research work is being carried out aiming at increasing the power absorption of OPD. This work proposes an alternative OPD using Gaussian source. The light excitations generates an electron-hole pair increasing the carrier’s density. The resulting electrons in the conduction band and the holes in the valence band can be drifted by an electric field, generating a current. This OPD device has very thin active organic layer less than 100nm. The Photonic Crystal (PC) used in the design has rectangular lattice structure with height of 120nm and width of 350nm. The Finite Difference Time Domain (FDTD) method is used for solving Maxwell’s equations in complex multi stack geometries. FDTD calculates the E and H fields everywhere in the computational domain (evolves in time domain), it provides animated displays of the electromagnetic field movement through the OPD model. The short circuit (Jsc) current obtained for the proposed OPD for with and without water soluble conjugate polymer placed above the emissive and incorporating PC in the device. This ensures high detectivity of the organic photo detector device.