An electrophosphorescent organic light emitting concentrator

We demonstrate threefold directional light concentration from an organic light-emitting diode luminaire for use in spot lighting and other applications where high intensity illumination is required. The concentrating luminaire comprises four triangular, large-area green electrophosphorescent organic light emitting diodes (PHOLEDs) deposited on plastic substrates and assembled into a pyramidal structure with an open base that serves as the light exit aperture. The PHOLED surfaces are highly reflective to direct the emission from the devices to the aperture independent of the original emission position within the pyramid. The far-field intensity profile of the concentrator has a ‘batwing’ distribution that meets the requirements for general lighting for uniform illumination of planar surfaces. A simple scheme for concentrating the light emission from organic LEDs could make them more useful for a variety of tasks. Jaesang Lee and colleagues from the University of Michigan in the USA assembled four triangular-shaped, green electrophosphorescent light-emitting devices (PHOLEDs) into a pyramid with an open base. The light exiting the base of the pyramid was found to have a luminance three times greater than that of a similarly sized conventional planar PHOLED. The enhancement is due to the high reflectivity of the PHOLED surfaces, which ensure that light generated anywhere in the pyramid is, after a number of reflections, directed out of the base of the structure. The researchers say that this concept can be applied to PHOLEDs with any colour of emission.