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This research is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering.
Tunable near-UV microcavity organic light-emitting diodes (OLEDs) that emit in the deep blue and ultraviolet light region have been developed using a novel approach. These devices address the growing need for portable compact near-UV sources for analytical tools as well as various biomedical and forensic applications. These are among the first OLEDs that emit in the near-UV region. In this new approach, the team tuned the thickness of the spacer layer of a nanometer wide microcavity, allowing them to tailor each individual OLED in the array to the desired narrow-band emission.
Significant LED performance improvements have been achieved by taking advantage of novel materials.An organic light emitting diode (OLED) requires at least one transparent electrode, which is most commonly indium tin oxide (ITO). While ITO is both transparent and a good electrical conductor, its light transmission differs from the other organic material layers used in the device, leading to internal reflections which reduce efficiency. Researchers replaced ITO with a special highly conductive polymer known as PEDOT:PSS.
A novel electrode architecture has led to a new way to make transparent electrical contacts. Typical ways of attaching a conductor to a non-metallic material allow you to see the electrode. However, for many applications, like light emitting diode (LED) displays, smart windows and solar cells, transparency to visible light is a requirement that conflicts with electrical conductance. Thinner films are more transparent, but less conductive. The new architecture consists of specially patterned nanoscale-thick metallic ribbons, standing on edge, supported by a polymer matrix.