Investigation of long-term stability of pentaeene thin-film transistors encapsulated with transparent SnO₂

The long-term stability of pentacene thin-film transistors (TFTs) encapsulated with a transparent SnO₂ thin-film prepared by ion beam assisted deposition (IBAD) was investigated. With a buffer layer of thermally evaporated 100 nm SnO₂ film deposited prior to IBAD process, our encapsulated OTFTs sustained its initial field-effect mobility up to one month and then gradually degraded showing only 37% reduction compared to 90% reduction of non-encapsulated OTFTs after 100 days in air ambient. The encapsulated OTFTs also exhibited superior on/off current ratio of over 10⁵ to that of the unprotected devices (∼10⁴) which was reduced from ∼10⁶ before aging. Therefore, the enhanced long-term stability of our encapsulated OTFTs should be attributed to well protection of permeation of H₂O and O₂ into the devices by the IBAD SnO₂ thin-film which could be used as an effective inorganic gas barrier for transparent organic electronic devices.