Active Matrix Driving Organic Light-Emitting Diode Panel Using Organic Thin-Film Transistors

Abstract

We developed an active matrix driving organic light-emitting diode (OLED) panel on a glass substrate using two organic thin-film transistors (OTFTs) per pixel, a switching OTFT and a driving OTFT. The OTFTs are bottom contact structures with the high-dielectric constant gate insulator tantalum oxide (Ta 2 O 5 , relative dielectric constant of 23) produced by anodization in ammonium adipate solution and with pentacene as the active layer. The W / L (where W and L are the OTFTs channel width and length, respectively) was 400 µm/10 µm for the switching OTFTs and 680 µm/10 µm for the driving OTFTs. The characteristics of the OTFTs were improved by treating the Ta 2 O 5 surface with hexamethyldisilazane (HMDS), so that the field-effect mobility was 2.0×10 -1 cm 2 V -1 s -1 and the current on/off ratio was 10 5 . A green phosphorescent dopant, tris(2-phenylpyridine)iridium [Ir(ppy) 3 ], was used for the OLED layer. The panel had 8×8 pixels and the aperture ratio was 27%. We confirmed a 16-gray-scale representation and a luminance of 400 cd/m 2 .