Role of Injection Barrier in Capacitance-Voltage Measurements of Organic Devices

Capacitance-voltage (C-V) measurements represent a very useful technique, however, its usage in organic devices has been a subject of debate because of the role played by the ambient-induced unintentional doping. In this letter, we show that, contrary to the current understanding, prolonged ambient exposure does not significantly increase the unintentional doping density of organic semiconductors (OSCs). Our C-V measurements and detailed numerical simulations clearly indicate that the observed dispersion in C-V characteristics can be attributed to the variation in the carrier injection barrier at the OSC/electrode interface. An analytical relation between the injection barrier and the response time is derived to describe the C-V characteristics of organic devices.