A New Pixel Circuit With Selectively Synchronized Dual-Gated IGZTO TFTs for AMOLED Displays

We developed an integrated dual-gate-driving thin-film transistor (TFT)-based compensation pixel circuit for active matrix organic light-emitting diode (AMOLED) displays to overcome the limitations of conventional pixel circuits that synchronize in only one direction. Our pixel circuit based on amorphous indium–gallium–zinc–tin oxide TFTs (a-IGZTO TFTs) utilizes selectively synchronized (SLT-Sync) dual-gate-driving TFTs to compensate for threshold voltage (
${V}_{{\mathrm {th}}}$
) variations and extend the input data range for precise control of emission current. We performed simulations to verify circuit performance and fabricated new and comparable pixel circuits to evaluate the simulation result. The new pixel circuit operates as a gate-synchronized (G-Sync) dual-gate TFT compensating for
${V}_{{\mathrm {th}}}$
variation, enabling more accurate and rapid sensing than a source-synchronized (S-Sync) dual-gate TFT. The field-effect mobility (
$\mu _{{\mathrm {FET}}}$
) of the new pixel was 1.4-fold than that of the latter dual-gate TFTs operating mode, and the emission current error rate on
${V}_{{\mathrm {th}}}$
variation (±0.5 V) was < 5.0%. The new pixel circuit behaved as an S-Sync dual-gate TFT during emission. The input data range is about 0.6 V greater than that of a G-Sync dual-gate TFT, due to the twofold increase in subthreshold swing (SS). Therefore, the new pixel circuit optimally balances fast
${V}_{{\mathrm {th}}}$
compensation and input data range expansion, and will find applications in high-resolution AMOLED displays by applying the SLT-Sync dual-gate TFTs, which operate in G-Sync and S-Sync modes as needed.