High performance of solution-processed SnO2 thin-film transistors by promotion of photo-exposure time-dependent carrier transport during the pre-annealing stage
We fabricate high-performance solution-processed SnO2 thin-film transistors (TFTs) exhibiting improved carrier transport features by exposing the ultraviolet/ozone (UV/O3) on the SnO2 film during the pre-annealing stage. The SnO2 layer is treated with different UV/O3-exposure times from 0 to 60 min before the post-annealing step. As UV/O3-exposure time increases from 0 to 30 min, the M-O-M (M, metal; and O, oxygen) network, mass density, and oxygen vacancies of films are enhanced. In contrast, the M-O-M network and mass density decrease, while the oxygen vacancies rather increase when the UV/O3-exposure time reaches 60 min beyond 30 min. The SnO2 (Sn4+) phase, thickness, and surface morphology of SnO2 films are not considerably changed regardless of UV/O3-exposure time. When the UV/O3-exposure time is 30 min, devices demonstrate superior field-effect mobility (10.1 cm2V−1s−1) at approximately 2 times higher than TFT without UV/O3-exposure. Furthermore, SnO2 TFT with UV/O3-exposure time for 30 min shows improved subthreshold-swing characteristics and a high on/off current ratio. These devices are adequate for use in high-resolution active-matrix LCDs or OLED displays that demand a high field-effect mobility (> 10 cm2V−2s−1) and on/off ratio (> 106).