Active‐matrix organic light‐emitting diode displays with indium gallium zinc oxide thin‐film transistors and normal, inverted, and transparent organic light‐emitting diodes

— Active-matrix organic light-emitting diode (AMOLED) displays have gained wide attention and are expected to dominate the flat-panel-display industry in the near future. However, organic light-emitting devices have stringent demands on the driving transistors due to their current-driving characteristics. In recent years, the oxide-semiconductor-based thin-film transistors (oxide TFTs) have also been widely investigated due to their various benefits. In this paper, the development and performance of oxide TFTs will be discussed. Specifically, effects of back-channel interface conditions on these devices will be investigated. The performance and bias stress stability of the oxide TFTs were improved by inserting a SiOx protection layer and an N2O plasma treatment on the back-channel interface. On the other hand, considering the n-type nature of oxide TFTs, 2.4-in. AMOLED displays with oxide TFTs and both normal and inverted OLEDs were developed and their reliability was studied. Results of the checkerboard stimuli tests show that the inverted OLEDs indeed have some advantages due to their suitable driving schemes. In addition, a novel 2.4-in. transparent AMOLED display with a high transparency of 45% and high resolution of 166 ppi was also demonstrated using all the transparent or semi-transparent materials, based on oxide-TFT technologies.