Abstract
Despite the intensive study on the promotion of device performance, the device physics regarding the effects of Schottky barrier on the charge injection in conjugated polymer transistors still need more discussions. Here, the indacenodithiophene–co-benzothiadiazole (IDT-BT) organic transistors (OFETs) with four different contact metals (Pt, Au, Cu, and Cr) were fabricated to explore the effects. Different Schottky barriers were achieved with the contact electrode’s work function (WF) varying. The ION/IOFF ratio of IDT-BT OFETs increased from 103 to 106 as the WF increased from 4.6 eV to 5.65 eV. The hole mobility also increased from 0.01 cm2V−1s−1 (for Cr) to 2.79 cm2V−1s−1 (for Pt) when the WF approached the highest occupied molecular orbital (HOMO) level of the conjugated polymer. Moreover, the threshold voltage and subthreshold swing of the devices both decreased with increasing the WF. These could be ascribed to the lowered Schottky barrier with WF, which promotes charge injection. The lowest Schottky barrier (0.123 eV) and contact resistance (1.06×104 Ω•cm) were achieved in the devices with Pt contacts, owing to the highest work function.
Highlights
Solution-processed organic field-effect transistors (OFETs) are promising for next-generation consumer electronics, because of the unique advantages of low cost, flexibility, and large-area fabrications (Liu et al, 2010; Jiang et al, 2019)
In order to improve the device performance for applications, much efforts have been paid to the material synthesis, film microstructure, device fabrication, and charge transport optimization of OFETs (Chen et al, 2012; Yuan et al, 2014; Uemura et al, 2016)
Charge injection, which occurs at the interface between metal and organic semiconductor (OSC), is one of the key factors to promote the device performance
Summary
Solution-processed organic field-effect transistors (OFETs) are promising for next-generation consumer electronics, because of the unique advantages of low cost, flexibility, and large-area fabrications (Liu et al, 2010; Jiang et al, 2019). Charge injection, which occurs at the interface between metal and organic semiconductor (OSC), is one of the key factors to promote the device performance. According to the Schottky–Mott limit, the Schottky barrier height can be roughly estimated from the difference between the contact electrode’s work function (WF) and the transporting energy level of the OSC (Tang et al, 2016). The Schottky barrier, the RC, and charge injection in indacenodithiophene–co-benzothiadiazole (IDT-BT) OFETs with four different contact metals (Pt, Au, Cu, and Cr) were studied.
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