Characteristics of contrast of active-matrix organic light-emitting diodes containing a black matrix and antireflection layers

We investigated the effects of black matrix (BM) and antireflection coating layers with adjusted a transmittance on the contrast of active-matrix organic light-emitting diodes (AMOLEDs). To achieve this, we coated the black matrix and the antireflection layers (with a transmittance of 45%) on an encapsulation glass. A black matrix with an optical density of 4.65 was patterned by means of photolithography and aligned above nonemissive areas to block ambient light. Then, after simulating the arrangement and thickness of multilayers composed of SiO2, TiO2 and Cr, these layers were deposited to provide antireflective properties in a broad visible wavelength region at a transmittance of 45%. The total thickness of the multilayers (namely, 183 nm) was below that of a circular polarizer (i.e., 200 μm). The ambient contrast ratios of AMOLEDs containing antireflection coating layers with 45% transmittance and circular polarizers were 2.5 and 2.6, respectively, at a brightness of 200 cd m−2 under ambient-light illumination (100,000 lx). These results indicate that circular polarizers can be substituted by a black matrix and antireflection coating layers with a transmittance of 45%.