Operation and Control of Flexible Display Pixel Circuits Under Mechanical Bending

Amorphous silicon (a-Si) thin-film transistor (TFT) technology has enabled the current flat-panel display industry and is used in a wide variety of consumer electronic products ranging from televisions to smart-phones. This technology has also been integrated onto plastic platforms and has enabled the fabrication of flexible a-Si based TFTs. When combined with light-emitting diodes (LEDs), low-power and high-brightness flexible emissive displays may be achieved. Due to its disordered structure, the electrical instability of a-Si TFTs can significantly limit the lifetime of the TFT operation. For flexible devices, the addition of mechanical strain due to bending of the substrate contributes to the electrical instability that limits the useful lifetime of devices. In this work, a novel 5-TFT and 1-capacitor (5T1C) pixel circuit has been proposed to mitigate the impact of the electrical instability of a-Si TFTs using a unique charge-transfer process. The proposed pixel circuit has been fabricated onto flexible substrate and the measurement results demonstrated less than 4% degradation of its output current after a 24-hour stress test under mechanical strain. Moreover, a significant reduction of external control-signal power consumption and complexity has also been demonstrated.