Data voltage compensation scheme for active-matrix organic light-emitting diode pixel circuits using double-gate indium-gallium-zinc oxide thin-film transistors

This study proposes a data voltage compensation scheme that addresses bottom-gate-to-source voltage (V_BGS) differences in double-gate indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) used in active-matrix organic light-emitting diode (AMOLED) pixel circuits. The compensation factor is derived from the pixel current equation and applied to the data voltage to correct the source voltage difference between the data writing and emission periods. To validate the approach, double-gate IGZO TFTs and diode-connected 6T1C pixel circuits were fabricated and evaluated under two bottom-gate conditions. The first ties the bottom-gate to the source and therefore can operate in depletion-mode, while the second applies a negative bottom-gate bias and can operate in enhancement-mode. The depletion-mode pixel shows a maximum current error of 35.8% at the 32nd gray level, while the enhancement-mode pixel reduces the maximum error to 9.6%. This value already reflects a maximum anode voltage (V_A) deviation of 0.047 V and the measured β range from − 0.42 to − 0.38, where β denotes the sensitivity of the threshold voltage (V_TH) to V_BGS. Consequently, the proposed scheme suppresses the V_BGS differences and enables accurate current driving across gray levels.