A polysilicon transistor based active matrix organic light emitting diode (AMOLED) pixel with high pixel to pixel luminance uniformity is reported. The new pixel powers the OLEDS with small constant currents to ensure consistent brightness and extended life. Excellent pixel to pixel current drive uniformity is obtained despite the threshold voltage variation inherent in polysilicon transistors. considerations in the design for high information content displays are discussed.
Articles you may be interested inAl2O3 multi-density layer structure as a moisture permeation barrier deposited by radio frequency remote plasma atomic layer deposition J. Appl. Phys. 115, 073502 (2014); 10.1063/1.4866001 Improvement in mechanical and barrier properties of polyethylene blown films using atomic layer deposition J. Vac. Sci. Technol. A 32, 01A126 (2014); 10.1116/1.4849075Radio frequency plasma power dependence of the moisture permeation barrier characteristics of Al2O3 films deposited by remote plasma atomic layer deposition Effect of early stage growth on moisture permeation of thin-film Al2O3 grown by atomic layer deposition on polymers J.
Recent discoveries of degradation mechanisms in organic light emitting diodes (OLEDs) are reviewed. One common observation regarding the OLED reliability is the gradual increase of the diode driving voltage under forward bias. This trend reverses when the bias polarity is reversed, and the initial driving voltage can be recovered almost completely. The mobile ions are proposed to explain the phenomenon. By solving a system of transient equations governing the mobile ion motion under an external field, we obtained the transient mobile ion distributions and their contribution to the driving voltage. We found that the mobile ion model with reasonable assumptions could very well explain the experimental results. Another advancement in the field is the utilization of a single organic alloy layer to improve the device lifetime. A typical organic alloy layer consists of a mixture of hole and electron transport materials. Significant lifetime improvement over heterojunction structures is achieved with comparable efficiency. The significant improvement in the device reliability is attributed to the elimination of the heterojunction interface and the minimization of the formation of Alq3 cations. The high efficiency is achieved due to the balanced carrier injection, transport and confined recombination in the device.
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