Investigation of Traps in Thin-Film Organic Semiconductors Using Differential Analysis of Steady-State Current–Voltage Characteristics

A study of traps in thin organic semiconductor films is described through the analysis of their impact on current voltage (J-V) characteristics of two terminal diode-like structures. The J-V characteristics follow a power law whose exponent exhibits voltage dependence as a result of change in trap occupancy with applied voltage. A method of analysis of J-V characteristics using the product of differential resistance and current is described which enables different unique regions of device characteristics to be visually delineated and facilitates extraction of threshold voltage, marking onset of trap-filled regime. Simulation results are presented to validate and highlight the usefulness of the proposed concepts and techniques. The experimental results obtained with polymers P3HT, blend of P3HT with phenyl C61 butyric acid methyl ester, and small molecule pentacene organic semiconductor are used to illustrate the insight offered by the proposed method. Both simulation and experimental results indicate that analysis based on double-log plots may lead to large overestimation of voltage marking onset of trap-filled regime.