The Impact of Solvents on the Performances of Solution‐Processed Indium Gallium Zinc Oxide Thin‐Film Transistors Using Nitrate Ligands

Herein, solution‐processed indium gallium zinc oxide (IGZO) thin‐film transistor (TFT) is fabricated utilizing metal nitrates as precursors, and the impact of nitrate ions in different solvents on the performances of IGZO TFT is demonstrated. During IGZO film fabrication, the nitrogen in nitrate species actually dopes into the film in the fashion of different chemical states depending on different solvents. When IGZO precursors dissolve in deionized water (DIW), due to the high polarity of the solvent, metal nitrates are completely dissociated, leading to the conversion of nitrates to nitrides in IGZO film. This nitrogen decreases the density of the interface trap states, thus improving the characteristics of the IGZO TFT. In contrast, when using 2‐methoxyethanol (2‐ME) as the solvent, nitrogen mainly forms nitrogen oxide and acts as a trap density that leads to the degradation of the device performances. By increasing the annealing temperature of IGZO film, nitrogen oxide can convert to metal nitride, resulting in enhanced device performance. The IGZO TFT fabricated using DIW as a solvent with 300 °C annealing temperature exhibits the saturation mobility of 2.5 cm² V⁻¹ s⁻¹ and I_on/off ratio of >10^6.5. Herein, a step is made toward the solvent effect on the performance of solution‐processed oxide TFT.