High-resolution a-IGZO TFT-based AMOLED pixel circuit enabling multiple OLED driving via the field sequential color method

This paper proposed a compact a-IGZO TFT-based active matrix organic light-emitting diode (AMOLED) pixel circuit driving multiple OLEDs. The pixel size was minimized using a single capacitor and field-sequential-color (FSC) driving, allowing one pixel to control two OLEDs, halving its effective size. However, these approaches constrain the threshold voltage (VTH) detection time to 1 horizontal (1H) time, and introducing subframes for FSC driving reduces 1H time compared to the conventional approach. This leads to pressing issues related to incomplete VTH sensing and the RC delay in the DATA line. Therefore, strategies to overcome these issues were also recommended. The findings revealed that the proposed circuit improves VTH detection accuracy in low gray levels by initializing the gate-source voltage of the driving TFT according to the gray level. This enhances the uniformity in low gray levels. Also, RC delay-induced nonuniformity was mitigated by extending the initialization stage to ensure the DATA line voltage stabilizes before data programming, minimizing the data storage distortion. Finally, the proposed circuit and its operation were verified through HSPICE and experimental measurements. The fabricated circuit, with a compact size of 39.3 μm × 39.3 μm, achieving 646 PPI, exhibited stable operation under the designed conditions.