Wolfgang Busselt

Lumiramic: a new phosphor technology for high performance solid state light sources

A new phosphor technology for phosphor converted light-emitting diodes (pcLEDs) is presented. A polycrystalline ceramic plate (LumiramicTM) of Ce (III) doped yttrium gadolinium aluminum garnet (Y,GdAG:Ce) is combined with a blue LED to produce white light in the range of 5000 K correlated color temperature. Scattering and light extraction means of the Lumiramic ceramic color converter plates enable production of reliable and efficient white pcLEDs. Measurement of the optical properties of the Lumiramic plates before the final LED assembly allows pick and place packaging with exact targeting of the desired white color point of the LED. Combination with a red phosphor powder layer, coated onto the Lumiramic plate, results in high quality white pcLEDs with any color temperature required for the general lighting market.

Subwavelength particle layers for improved light outcoupling of OLEDs

Subwavelength silica particle layers have been applied between glass and thin film luminescent layers of Alq3 and a polymer MEH-PPV layer, respectively. The layers acted as a randomised two-dimensional diffraction lattice, which increased the fraction of emitted power from thin film organic layers into air. In contrast to perfectly ordered structures strong interference emission patterns did not occur. Still, an optical feedback of the particle layer on the emission spectrum could be observed, which can be used to improve colour saturation for blue and green emission and to increase the lumen efficiency for red emission, without changing the colour point of the red emitter. In photoluminescence experiments a gain factor of 3 and 2.5 in light outcoupling was realized for Alq3 and MEH-PPV layers, respectively. With a MEH-PPV polymer OLED device an efficiency gain of 30 to 40 % has been realized in electroluminescence.