Low-voltage organic single-crystal field-effect transistors and inverters enabled by a solution processable high-k dielectric

Abstract

Low voltage operation is of critical importance for organic field effect transistors (OFETs) in next-generation flexible and wearable electronics, wherein the use of high-k dielectrics has been proved to be the most promising way. However, high-k dielectrics typically lead to a substantial reduction of device performance, including the key figures of merit of mobility and on/off ratio. The realization of low voltage operation at the cost of device performance blocked their practical applications. To date, it is still challenging to construct low-voltage high-performance OFETs. Herein, a novel structured dielectric (i.e., hafnium–aluminum binary metal oxide, HAO) was developed using a designed “nitrogen–air–nitrogen (NAN)” process under high-temperature annealing, which exhibits high permittivity, appropriate bonding, atomically flat surface, excellent insulating properties, and homogeneous amorphous characteristics. As a result, the OFET-based HAO dielectric demonstrated promising performances, including the mobility comparable to those prepared using an octadecyltrichlorosilane (OTS)-modified SiO₂ substrate, a subthreshold slope approaching a theoretical limit of 60 mV dec⁻¹, an operating voltage of 3 V, and an on/off ratio of 10⁷. Based on these OFETs, complementary-like inverters were constructed successfully, which showed a remarkably high gain of 172 (V_DD = 4 V). The development of high quality high-k dielectrics paves the way for constructing low-power optoelectronic devices for wearable electronics.