Low-temperature, high-performance solution-processed metal oxide thin-film transistors formed by a 'sol-gel on chip' process

At present there is no 'ideal' thin-film transistor technology for demanding display applications, such as organic light-emitting diode displays, that allows combining the low-temperature, solution-processability offered by organic semiconductors with the high level of performance achievable with microcrystalline silicon(1). N-type amorphous mixed metal oxide semiconductors, such as ternary oxides Mx(1)My(2)O(z), where M-1 and M-2 are metals such as In, Ga, Sn, or Zn, have recently gained momentum because of their high carrier mobility and stability(2,3) and good optical transparency, but they are mostly deposited by sputtering. So far no route is available for forming high-performance mixed oxide materials from solution at low process temperatures <250 degrees C. Ionic mixed metal oxides should in principle be ideal candidates for solution-processable materials because the conduction band states derived from metal s-orbitals are relatively insensitive to the presence of structural disorder and high charge carrier mobilities are achievable in amorphous structures(2). Here we report the formation of amorphous metal oxide semiconducting thin-films using a 'sol-gel on chip' hydrolysis approach from soluble metal alkoxide precursors, which affords unprecedented high field-effect mobilities of 10 cm(2) V-1 s(-1), reproducible and stable turn-on voltages V-on approximate to 0 V and high operational stability at maximum process temperatures as low as 230 degrees C.