ИСТИНА

Organic field-effect transistors (OFET) are perspective basic elements for low-cost, large-area electronic devices. The crucial parameter that determines the OFET performance is the charge carrier mobility. The common method of mobility measurement in OFET consists in approximation of the transfer characteristics by Shockley equations in the linear and saturation regimes. However, this method can lead to incorrect estimation of charge mobility in organic semiconductor. In the common top-contacts and bottom-gate OFET geometry, the current needs to pass through the thickness of organic semiconductor layer under the source and drain contacts, and the voltage can drop across the layer due to space charge limited current (SCLC). In this work, we study how the SCLC under the source and drain electrodes affects the apparent mobility determined from the transfer characteristics. We developed both numerical and analytical models of OFET with SCLC under the contacts and found how the fitted OFET mobility changes with the active layer thickness. The modeling showed that the apparent OFET mobility drops with increasing the active layer thickness and decreasing the transverse charge mobility (across the active layer). These findings allow evaluation of the intrinsic OFET mobility and provide guidelines for further improvement of OFET performance. This work was supported by Russian Science Foundation (grant 15-12-30031).