Pixel circuit with P-type low-temperature polycrystalline silicon thin-film transistor for micro light-emitting diode displays using pulse width modulation

Herein, we present a novel low-temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) pixel circuit for amicro light-emitting diode (μLED) display based on pulse width modulation (PWM). By adopting PWM, we could achieve 10-bit gray levels of μLED without wavelength shift, which is a challenge in the realization of μLEDs. Furthermore, the proposed circuit compensated for the variation in threshold voltage (VTH) without an external sensing system. We simulated the error rate of the μLED emission time of the proposed pixel circuit depending on the VTH change. We measured the wavelength shift of the μLED using the fabricated circuit. This shift in PWM was smaller than that in pulse amplitude modulation (PAM). Consequently, the proposed pixel circuit could overcome screen distortions caused by color shifts of μLED displays using PWM techniques.