High-performance n- and p-type organic single-crystal field-effect transistors with an air-gap dielectric towards anti-ambipolar transport

Abstract

The dielectric property has a significant effect on the performance of organic field-effect transistors (OFETs); therefore, a number of studies reported on dielectrics are focused on the development of high-performance OFETs. In this study, an air-gap dielectric was used to replace SiO₂ as a low-defect insulating layer to improve the performance of OFETs. Based on the air-gap dielectric, a single-crystal ribbon of a thiophene-based quinoidal compound (TTT-CN) was first prepared, which exhibited a high electron mobility of 2.17 cm² V⁻¹ s⁻¹ in air. In order to build p–n heterojunction devices, a p-type single-crystal transistor was developed, which showed a balanced mobility of 2.45 cm² V⁻¹ s⁻¹, comparable to that of n-type transistors. Furthermore, the gate-tunable anti-ambipolar characteristics of FETs were demonstrated based on the p–n heterojunction obtained by combining the cross-overlapped n- and p-type single crystals with the air-gap dielectric. The reduction in the number of trap states on the air-gap layer resulted in a smaller hysteresis effect, and the value of ΔV_peak effectively reduced from 28.5 V to 6 V in anti-ambipolar transistors.