Impacts of Minority Charge Carrier Injection on the Negative Capacitance, Steady‐State Current, and Transient Current of a Single‐Layer Organic Semiconductor Device

Abstract

AbstractSpace charge limited current theory is often used to analyze electrical characteristics of single‐layer organic semiconductor devices using Ohmic and Schottky contacts for injection of majority and minority carriers, respectively. However, significant deviations from this theory in the current density–voltage and capacitance–frequency characteristics of the devices have been frequently observed. For instance, the increase in current density is not proportional to the voltage‐square and the capacitance becomes negative at low frequencies. Here, it is presented that the minority carriers in a single‐layer device despite a large Schottky barrier give rise to the negative capacitance at low frequencies and the drastic increase in steady‐state current density at high voltages. The leaky electrons at the hole‐dominant device are demonstrated by inserting an electron scavenger layer. The transient current of the device shows the injection and transport properties of electrons by low and dispersive mobility. The negative capacitance of the device at low frequencies is a response of the minority carrier injection. The current density increases drastically at high voltages due to the increasing minority carriers that redistribute the electric field, which is not shown at low voltages. Finally, the device model incorporating minority charge carriers fully describes the electrical characteristics of the device.