Spin-Coated CdS Thin Films for n-Channel Thin Film Transistors

Low-cost and high-performance materials fabricated at low temperatures via solution processes are of great interest in the field of printable and flexible electronics. We have investigated a new solution-based approach to the synthesis of semiconducting chalcogenide films for use in thin-film transistor (TFT) devices in an attempt to develop a simple and robust solution process for the synthesis of inorganic semiconductors. Our material design strategy is to use a sol−gel reaction for the deposition of a spin-coated CdS film that can then be converted to a xerogel material. By carrying out the spin-coating of a L 2 Cd(S(CO)CH 3 ) 2 ( L = 3,5-lutidine) precursor, which condenses at low temperatures to form a CdS network, and then hard-baking at 300 °C under atmospheric pressure, microscopically flat films were successfully obtained. To determine the field effect mobilities of the spin-coated CdS films, we constructed TFTs with an inverted structure consisting of Mo gate electrodes and ZrO 2 gate dielectrics. These devices exhibited n-channel TFT characteristics with an excellent field-effect mobility (a saturation mobility of ∼48 cm 2 V −1 s −1 ) and a low voltage operation (<5 V), indicating that these semiconducting thin film materials can be used in low-cost and high-performance printable electronics.