Influence of the semiconductor oxidation potential on the operational stability of organic field-effect transistors

Abstract

During prolonged application of a gate bias, organic field-effect transistors show a gradual shift of the threshold voltage towards the applied gate bias voltage. The shift follows a stretched-exponential time dependence governed by a relaxation time. Here, we show that a thermodynamic analysis reproduces the observed exponential dependence of the relaxation time on the oxidation potential of the semiconductor. The good fit with the experimental data validates the underlying assumptions. It demonstrates that this operational instability is a straightforward thermodynamically driven process that can only be eliminated by eliminating water from the transistor.

Effects of Ambient Gases on the Electrical Performance of Solution-Processed C8-BTBT Thin-Film Transistors

“…In addition, mobile charges in the semiconductor are slowly replaced by immobile charges at the SiO 2 surface that can reversibly migrate into bulk SiO 2 . Therefore, exposure to air for a long time, constant absorption and interaction of moisture will lead to increased transistor instability [27] and reduce its carrier mobility.…”

Operational Stability of Organic Field‐Effect Transistors

“…[54] The characteristic time t 0 of the proton migration mechanism is given by Equation (11). Since the diffusion coefficient D in this equation is related to diffusion of protons in the SiO 2 it does Close inspection of the time evolution of the transfer curve in Figure 1a shows that during stress the slope of this curve in its linear region slightly decreases, pointing at a decreased charge-carrier mobility.…”

“…However, the rate constant of reaction (5) will depend strongly on the oxidation potential of the semiconductor, which is directly related to the semiconductor's highest occupied molecular orbital, E HOMO . One can derive the following expression for α: [54] α…”

Scanning Kelvin Probe Microscopy Investigation of the Role of Minority Carriers on the Switching Characteristics of Organic Field‐Effect Transistors

“…The extracted hole mobility is very low compared to the electron mobility, in fact it is so low that no hole current–voltage characteristics can be measured in the n‐type semiconductors. We speculate that this may be due to extrinsic trapping of holes arising from ambient species, as expected for a semiconductor with a rather deep HOMO (about 6.3 eV) . So, our SKPM measurements and modeling methods thus provide an elegant and direct way to probe the hole transport in n‐type semiconductors, or more generally, the transport of the minority charge carriers in organic semiconductors.…”