Flat-[Ga13(μ3-OH)6(μ-OH)18(H2O)24](NO3)15(Ga13) and heterometallic [Ga13-xInx(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 InxGa13-xOysemiconducting films in <2 h. Raman spectroscopy and ¹H-NMR spectroscopy confirm the presence of [Ga13-xInx(μ3-OH)6(μ-OH)18(H2O)24(NO3)15] clusters. Bottom-gate thin-film transistors were fabricated using ∼15 nm-thick Ga13-xInxOyfilms 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^-2V^-1s^-1which was more than twice that of transistors fabricated from control solutions with the simple nitrate salt precursors of ∼2 cm^-2V^-1s^-1. Electrochemical cluster synthesis thus provides a simple and direct route to aqueous precursors for solution-processed inorganic electronics.