Electrochemical synthesis of flat-[Ga13−xInx(μ3-OH)6(μ-OH)18(H2O)24(NO3)15] clusters as aqueous precursors for solution-processed semiconductors

Flat-[Ga₁₃(μ₃-OH)₆(μ-OH)₁₈(H₂O)₂₄](NO₃)₁₅ (Ga₁₃) and heterometallic [Ga_13−xIn_x(μ₃-OH)₆(μ-OH)₁₈(H₂O)₂₄](NO₃)₁₅ (x = 5, 4) clusters were synthesized by the electrolysis of metal nitrate salt solutions to directly form, without purification, aqueous precursor inks for In_xGa_13−xO_y semiconducting films in <2 h. Raman spectroscopy and ¹H-NMR spectroscopy confirm the presence of [Ga_13−xIn_x(μ₃-OH)₆(μ-OH)₁₈(H₂O)₂₄(NO₃)₁₅] clusters. Bottom-gate thin-film transistors were fabricated using ∼15 nm-thick Ga_13−xIn_xO_y films as the active channel layer, displaying turn-on voltages of −2 V, and on/off current ratios greater than 10⁶. The average channel mobility of the transistors fabricated from the cluster solutions generated by electrolysis was ∼5 cm⁻² V⁻¹s⁻¹ which was more than twice that of transistors fabricated from control solutions with the simple nitrate salt precursors of ∼2 cm⁻² V⁻¹s⁻¹. Electrochemical cluster synthesis thus provides a simple and direct route to aqueous precursors for solution-processed inorganic electronics. [ABSTRACT FROM AUTHOR]