The fabrication of color-tunable organic light-emitting diode displays via solution processing

Electroluminescent devices based on organic semiconductors have attracted significant attention owing to their promising applications in flat-panel displays. The conventional display pixel consisting of side-by-side arrayed red, green and blue subpixels represents the mature technology but bears an intrinsic deficiency of a low pixel density. Constructing an individual color-tunable pixel that comprises vertically stacked subpixels is considered an advanced technology. Although color-tunable organic light-emitting diodes (OLEDs) have been fabricated using the vacuum deposition of small molecules, the solution processing of conjugated polymers would enable a much simpler and inexpensive manufacturing process. Here we present the all-solution processing of color-tunable OLEDs comprising two vertically stacked polymer emitters. A thin layer of highly conducting and transparent silver nanowires is introduced as the intermediate charge injection contact, which allows the emission spectrum and intensity of the tandem devices to be seamlessly manipulated. To demonstrate a viable application of this technology, a 4-by-4 pixelated matrix color-tunable display was fabricated. Using a tandem design of stacked organic emitters, color-tunable organic light-emitting diodes (OLEDs) have been made by solution processing. Conventional displays consisting of red, green and blue pixels arranged in a two-dimensional array suffer from limited resolution. Now, scientists in Germany and China have demonstrated a 4 × 4 pixel matrix color-tunable display that uses the color-tunable OLEDs as pixels. Each pixel consists of two OLEDs, which are stacked vertically and emit different colors. A thin layer of conductive silver nanowires is used as a transparent intermediate charge-injection electrode, which allows the emission intensity and color of the tandem device to be controlled. Compared with the conventional approach, the stacked approach is easier to manufacture and allows for smaller pixels and thus a higher resolution display.