Air processed Cs₂AgBiBr₆ lead-free double perovskite high-mobility thin-film field-effect transistors

This study focuses on the fabrication and characterization of Cs₂AgBiBr₆ double perovskite thin film for field-effect transistor (FET) applications. The Cs₂AgBiBr₆ thin films were fabricated using a solution process technique and the observed XRD patterns demonstrate no diffraction peaks of secondary phases, which confirm the phase-pure crystalline nature. The average grain sizes of the spin-deposited film were also calculated by analysing the statistics of grain size in the SEM image and was found to be around 412 (± 44) nm, and larger grain size was also confirmed by the XRD measurements. FETs with different channel lengths of Cs₂AgBiBr₆ thin films were fabricated, under ambient conditions, on heavily doped p-type Si substrate with a 300 nm thermally grown SiO₂ dielectric. The fabricated Cs₂AgBiBr₆ FETs showed a p-type nature with a positive threshold voltage. The on-current, threshold voltage and hole-mobility of the FETs decreased with increasing channel length. A high average hole mobility of 0.29 cm² s^-1 V^-1 was obtained for the FETs with a channel length of 30 µm, and the hole-mobility was reduced by an order of magnitude (0.012 cm² s^-1 V^-1) when the channel length was doubled. The on-current and hole-mobility of Cs₂AgBiBr₆ FETs followed a power fit, which confirmed the dominance of channel length in electrostatic gating in Cs₂AgBiBr₆ FETs. A very high-hole mobility observed in FET could be attributed to the much larger grain size of the Cs₂AgBiBr₆ film made in this work.