LTPS AM-OLED Display Consisting of Two-TFTs/One-Capacitor Pixel Circuits for Producing High-Uniformity Images

A method for generating threshold voltage (V_th) of thin-film transistors (TFTs) is proposed. This method is applied to the simplest pixel circuit, namely, one composed of two TFTs, a drive TFT and an address TFT, and one capacitor [i.e., two TFTs and one capacitor configuration], of active-matrix organic light-emitting diode (AM-OLED) displays. It involves two steps. First, source voltage of the drive TFT is quickly and precisely detected under the condition that carriers, namely holes, in the drive TFT are detrapped. Second, a simple subtraction and bit-shift operation are executed using the detected source voltage of the drive TFT. A prototype 3.8-in 480 × 320-pixel AM-OLED display was developed to confirm that a V_th-distribution image produced by this method corresponds to nonuniform images of AM-OLED displays. Furthermore, the AM-OLED display produced high-uniformity images when the V_th distribution was compensated by the proposed method.