Hans Peter Loebl

Investigation of FIrpic in PhOLEDs via LC/MS technique

The commercial breakthrough of phosphorescent organic white light sources is presently hampered due to the unavailability of a stable blue phosphorescent emitter material. Moreover, only few analytical investigations have been made regarding the chemical degradation of the phosphorescent emitter materials during the processing or the operation of the devices.Organic light emitting devices (OLEDs) containing phosphorescent metal complexes with iridium as central ion were investigated. Special attention was paid to the chemical degradation of the material. The devices were analyzed by means of high performance liquid chromatography coupled with mass spectrometry (HPLC/MS). Electron spray ionization (ESI) was employed as ionization source. Isomerization phenomena of the blue-green emitting heteroleptic iridium complex FIrpic could be observed after the device manufacture and after operation. These findings could give hints on the mechanisms that influence the lifetime of PhOLEDs based on FIrpic or similar blue emitters.

Narrow band bulk acoustic wave filters

Bulk acoustic wave (BAW) filters are competing successfully in the range of 800 MHz to 10 GHz with SAW filters. USPCS and UMTS filters require a bandwidth of 60 MHz at approximately 2 GHz (fractional BW /spl Delta/f/f/spl ap/3%). This can be realized by optimum design and high quality piezoelectric AlN which allows figure of merit, k/sup 2/Q, values of up to 100. On the other hand, relatively narrow band solidly mounted BAW filters can also be made. We present a narrow band filter with approximately 8 MHz bandwidth at a center frequency of approximately 1.2 GHz (fractional BW /spl Delta/f/f/spl ap/0.5%). The resonators required for narrow band filters can be designed to have extremely good temperature characteristics (down to -2 ppm/K) and high Q (>1000), which makes such devices interesting for new applications.

Filter system with bulk wave resonator having a reflection layer composition that varies with the layer thickness

The invention relates to a filter device equipped with at least one bulk acoustic wave resonator, which comprises a resonator unit and a reflection unit. The resonator unit comprises a first (3) and a second electrode (5) together with a textured piezoelectric layer (4) between the first (3) and second (5) electrodes.