The effect of the trap density and depth on the current bistability in organic bistable devices

Abstract

Current-voltage (I-V) characteristics and trap densities of organic bistable devices (OBDs) fabricated utilizing SnO2 nanoparticles embedded in a polymer layer in the framework of the space-charge limited current (SCLC) model were calculated in order to investigate the transition mechanisms of the states and to compare the values with the experimental I-V curves of the fabricated OBDs. The effect of the trap density and depth on the current bistability in OBDs with a single layer was simulated using the Poisson equation, the drift equation, and the single-level trap model. The slope of the current variation for OBDs in the low conductivity (OFF) state was between 2 and 3, and that for the devices in the high conductivity (ON) state was 2, indicative of the appearance of a SCLC. The ON/OFF conductivity ratio of the OBDs was approximately 102. Because the electron occupation probability increased with increasing trap depth, the number of electrons trapped in the organic layer increased, resulting in an increase in the ON/OFF ratio of the current bistability. The experimental I-V curves for OBDs were in reasonable agreement with the theoretical I-V curves obtained by using a simulation method.