Interface Modification for Tuning the Contact Resistance of Metal/Organic Semiconductor Junctions

Abstract

Abstract:As the performance of organic field-effect transistors improves, the limitation due to charge carrier injection at source and drain electrodes becomes crucial. This review describes the various solutions that have been developed to work around this issue. The most widespread method consists of interposing between the electrodes and the organic semiconductor film a self-assembled monolayer made of an appropriate reactive molecule. In that case, the reduction of the contact resistance may come either from an improved morphology of the semiconductor film, or to a better energy level alignment at the interface with the electrode. The respective inference of both aspects is discussed. Alternative ways to reduce the contact resistance by an appropriate surface treatment of the electrodes prior to the deposition of the semiconductor are also presented.

Motion-Programmed Bar-Coating Method with Controlled Gap for High-Speed Scalable Preparation of Highly Crystalline Organic Semiconductor Thin Films

“…Although the superior crystalline structure would be the primary factor for explaining the very high hole mobility, the PTAA bottom layer was also shown to be useful for lowering the charge injection barrier by forming the cascade energy structure (Figure S17). 36 The contact resistance estimated by the Y-function method was largely reduced from 2908 Ω cm (for OTFT prepared with homo C 8 -BTBT films) to 1474 Ω cm (for the device with the blend film; Figure S18). 37 Furthermore, the bar-coated devices showed excellent device-to-device uniformity and long-term environmental stability as well.…”

Reducing the contact resistance in bottom-contact-type organic field-effect transitors using an AgO x interface layer

“…For this reason, several studies have reported various methodologies for reducing the contact resistance (R c ) between the organic active layer and the source-drain (S-D) electrodes. [12][13][14][15][16][17][18][19][20] The insertion of a thin metal-oxide layer with a high work function (WF) as a hole-injection layer in OFETs has been shown to be an easy and effective way to reduce R c . [21][22][23][24] For example, Kumaki et al have demonstrated that inserting an ultrathin molybdenum oxide (MoO x ) layer in conventional pentacene bottomcontact (BC) transistors could reduce R c by nearly one order of magnitude.…”

Morphological impact of insulator on inkjet-printed transistor

“…If we check the leakage current by making, as previously, a zoom on the starting output characteristics of the OFETs at very low values of the drain-source voltage VDS (Figure 7c and d) Indeed, it is well known that in bottom contact structures, the electrodes engineering is one of the key parameter acting on charge injection into OSC layer. [36,38] In particular, thick electrodes disturb the continuous growth of a single-phase domain in active layer. [39] Moreover, it has also been observed that thick electrodes can also induced high access resistance due to incomplete step coverage at the contact edge.…”

“…This means we need higher gate-source voltage to compensate for the effect of the drain electric field and to get the starting negative drain current. Indeed, it is well known that in bottom contact structures, electrode engineering is one of the key parameters acting on charge injection into the OSC layer [36,37]. In particular, thick electrodes disturb the continuous growth of a single-phase domain in the active layer [38].…”