Philipp Stössel

Deep blue widely tunable organic solid-state laser based on a spirobifluorene derivative

We report on amplified spontaneous emission and optically pumped deep blue lasing in the organic spirobifluorene derivative 2,7-bis(biphenyl-4-yl)-2′,7′-di-tert-butyl-9,9′-spirobifluorene. Solid-state lasing is observed in thin films of this material deposited on a distributed-feedback (DFB) grating substrate. The laser wavelength can be tuned from 401.5 to 434.2 nm depending on the grating period of the Bragg reflector. The blue edge of this interval at 401.5 nm makes this laser an extremely short wavelength organic DFB laser. When pumping with a pulsed nitrogen laser at 337 nm, we observe a laser threshold energy density of 83 μJ/cm2. These results render this spiro compound an excellent candidate for blue-emitting diode lasers.

Light-emitting polymer materials for full-color displays

In the last few years, industrial research into materials fulfilling the needs of the maturing OLED display industry has intensified considerably. A first generation of polymers (phenyl-PPVs) is now being commercially exploited in first monochrome polymer LED displays. Nevertheless, due to market interest, there is a huge demand for materials for full-color OLED displays. After giving some initial results on our work in this field at last years SPIE, we will report on the progress in the development of polymers for red, green, and blue emission. Our main focus here lies on the improvement of the properties of various polymers derived from the spiro-bifluorene core. Depending on the color, the main issues vary strongly: Whereas e.g. for BLUE materials, efficiency, color coordinates, and processibility fulfill already commercial demands, operational lifetime still needs to be improved strongly. For RED materials, in contrast, the operational lifetime is already excellent, whereas the efficiency and the driving current still need to be improved. For GREEN acquiring saturated emission, whilst maintaining the other properties (high efficiency, long operational lifetime), is still challenging. Also, we will report on advances in full-color patterning, especially techniques based on Ink-Jet Printing.