Extended lifetime of pentacene thin-film transistor with polyvinyl alcohol (PVA)/layered silicate nanocomposite passivation layer

We prepared a novel organic passivation material to protect organic thin-film transistors (OTFTs) from H2O and O2 using a polyvinyl alcohol (PVA)/hydrophilic layered silicate (HLS) nanocomposite system. Using up to a 3 wt% layered silicate to PVA weight concentration, a highly homogeneous nanocomposite solution was prepared. In addition, a PVA/HLS nanocomposite solution formed a smooth film layer by the spin-coating method with RMS surface roughness of about 1 nm. An OTFT device with PVA passivation showed a decrease of 23% in field effect mobility after passivation. However, a pentacene TFT device with PVA/HLS nanocomposite passivation showed no significant initial performance drop after passivation, and mobility was even slightly improved. Pentacene TFT-passivated PVA/HLS showed 2860 h of TFT lifetime (the time required to reduce the mobility by one-half of the initial mobility after passivation), which is almost twice the lifetime of pentacene TFT with PVA passivation (1320 h). We propose that a layered silicate containing PVA nanocomposite film can be used as an effective organic passivation layer in an OTFT.