Metal salt-derived In-Ga-Zn-O semiconductors incorporating formamide as a novel co-solvent for producing solution-processed, electrohydrodynamic-jet printed, high performance oxide transistors

We report the previously unrecognized co-solvent, formamide (FA), which can comprehensively improve both the device performance and bias stability of metal salt-derived, solution-processed In-Ga-Zn-O (IGZO) TFTs. By incorporating FA in IGZO precursor solutions, the chemical structures are tailored adequately for reducing the content of hydroxide and encouraging the oxygen vacancy formation, which has not been fulfilled in conventional chemical/physical approaches. Owing to such distinct chemical structural evolution, the field-effect mobility is enhanced dramatically by a factor of 4.3 (from 2.4 to 10.4 cm² V ^-1 s^-1), and the threshold voltage shift during a positive-bias stress test is suppressed effectively by a factor of 2.3 (from 9.3 to 4.1 V) for unpassivated devices. The addition of formamide to IGZO precursor solutions also facilitates electrohydrodynamic-jet (e-jet) printability, with which the directly printed device with a channel width of ∼30 μm is demonstrated successfully. In addition, a high performance, solution-processed IGZO transistor with a mobility of 50 cm² V^-1 s ^-1 is suggested through coupling a FA-added IGZO oxide semiconductor with a solution-processed zirconium aluminum oxide ((Zr,Al)₂O _x) gate dielectric.