High-Performance Fully Solution-Processed Oxide Thin-Film Transistors via Photo-Assisted Role Tuning of InZnO

Abstract

The realization of next-generation flexible electronics involves the successful integration of functional solutionprocessed materials using simple and low-temperature fabrication techniques that are applicable to heat-sensitive substrates. Although there are numerous studies on the single solutionprocessed layer in an oxide thin-film transistor (TFT) structure, integrating all solution-based layers remains challenging. Here, fully solution-processed amorphous InZnO (a-IZO) TFTs were demonstrated utilizing the solution-based channel, gate insulator, and electrodes with a maximum fabrication temperature of 300 °C. Particularly, a single layer of a-IZO was used as both the channel and the source/drain electrode layer by selectively tuning the role of a-IZO as a semiconductor or a conductor through photoassisted treatments. By employing a self-aligned TFT structure, the a-IZO electrodes were functionalized by UV irradiation and excimer laser annealing (ELA). The fully solution-processed a-IZO TFTs exhibited high performance with an average mobility of up to 38 cm 2 V −1 s −1 , which surpasses those of previously reported approaches for fully solution-processed oxide TFTs. Moreover, the overall device performance, including a subthreshold swing of 225 mV dec −1 and an on-voltage of −0.4 V, is comparable to those of vacuum-processed oxide TFTs. In-depth analyses suggest that the successful functionalization of the a-IZO semiconductor into conductive electrodes is due to oxygen vacancy generation after UV treatment and subsequent crystallization and densification of the irradiated a-IZO areas after ELA. The demonstration of simple low-temperature photofunctionalization of solution-based oxide materials can be applied to 3D printing and can advance the high-throughput display manufacturing such as roll-to-roll processing.

Recent Advances in Thin Film Electronic Devices

“…The destruction rate of M-O bond and the oxidation rate of metal elements together determine the concentration of oxygen vacancies in the thin films. Usually, the formation of oxygen vacancies is often accompanied by the generation of electrons, which increases the carrier concentration of metal oxide films [68,91]. The increase of oxygen vacancy concentration causes high carrier concentration to form an electron transport path near the conduction band, thus increasing the mobility of TFT devices and reducing the threshold voltage [76,[92][93][94][95].…”

Solution-Processed Silicon Doped Tin Oxide Thin Films and Thin-Film Transistors Based on Tetraethyl Orthosilicate

“…Si 4+ has the same valence state as Sn 4+ , and will not introduce new charges into SnO 2 . In addition, the binding energy of Si-O (799.6 kJ/mol) is higher than that of Sn-O (531.8 kJ/mol), and the Lewis acid strength of Si (8.096) is also significantly higher than that of Sn (1.617), which makes Si a superior oxygen binder to suppress the formation of V O [27][28][29]. Liu et al [30] fabricated silicon doped SnO 2 -TFTs (STO-TFTs) by sputtering, controlling the V O concentration with Si, and the best device performance was obtained with 1 wt.% Si: the saturation mobility (µ sat) was 6.38 cm 2 /(V•s), the on/off current ratio (I on /I off ) was 1.44 × 10 7 , and the subthreshold swing (SS) was 0.77 V/Dec.…”

As-Grown Crystalline InGaZnO by Spray Pyrolysis on a Flexible Substrate for a Thin-Film Transistor with Excellent Stability

“…Therefore, extensive research has been conducted on solution-processed MOS TFTs. The popular methods for the solution process are spray pyrolysis, spin coating, and inkjet printing. − Among them, the spray pyrolysis method is promising because of the advantage of large-area uniformity . Note that the spray pyrolysis method eliminates the need for additional thermal annealing for crystallization.…”