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A novel digitally driven pixel circuit for active‐matrix organic light‐emitting diode (OLED) microdisplays is proposed and evaluated. This circuit supports both pulse width modulation and pulse density modulation digital drive approaches. Only three transistors and one capacitor are required per pixel for the proposed circuit. A current mirror is used to compensate for the pixel current changes that occur because of the degradation of the OLEDs over time. The compensation current depends on the potential of the common cathode, the properties of the current mirror, and the Width/Length (W/L) ratio of the drive transistor. The proposed digital pixel circuit also has advantages in circuit layout compared with analog pixel circuits.

The paper puts forward a method on controlling the AM-OLED panel to display image with high gray scale levels. It also gives an ASIC design sample to implement this method. A twenty sub-fields scan scheme has been taken into use in the chip to display 256 gray scale levels on a QVGA resolution AM-OLED display screen. The functions of image scaling and rotating have also been implemented for multiply application. The simulation and chip test result show that the chip design has met the design requirements.

In order to investigate the feasibility of gating organic field-effect transistors (OFETs) using a photosensitive photoresist material, pentacene-based OFETs were fabricated on indium tin oxide (ITO) glass. The gate dielectric was found to be easily patterned by spin coating and UV exposure, and has an excellent surface roughness of 0.22 nm and good insulating properties, resulting in a low leakage current (49 nA at 2 MV/cm) at a dielectric thickness of 290 nm. The OFET with photopatterned gate dielectric exhibited good electric characteristics, including a high field-effect mobility of 0.15 cm2/Vs, a threshold voltage of -9.9 V, and on/off current ratio of ~104. The high matching of surface free energy between the gate dielectric and pentacene is proved to be contributed to the good performance of the device.