49.3: A 200-dpi Transparent a-Si TFT Active-Matrix Phosphorescent OLED Display

We have fabricated a 120×160 high‐resolution (200dpi) a‐Si TFT active‐matrix transparent phosphorescent OLED (PHOLED™) display with novel pixel architecture to maximize transparency and aperture ratio and also ensure comparable light emission from both sides of the display. The a‐Si backplane was selected as the technology that would most easily enable the pathway toward achieving high‐resolution flexible transparent AMOLEDs (T‐AMOLEDs) on polymeric substrates. A‐Si TFTs are preferred for fabrication on polymeric substrates since lower process temperatures can be used in comparison to poly‐Si TFT processes. As a TOLED generally emits less light from a transparent cathode than anode, a standard 2T pixel was designed with both an opaque, reflective anode region on top of the TFTs as well as a conventional transparent ITO anode to equal the emission from both contacts. This design achieves a total pixel aperture ratio of 64% with a display transparency of 23% in the off‐state.