The Effect of Inorganic/Organic Hybrid Quantum-Well Structure on Efficient White Organic Light Emitting Devices
In this study, the effect of MQW structures adopting inorganic material (sodium fluoride) has been demonstrated. Brightness, current efficiency was significantly enhanced with a NaF/NPB MQW structure being inserted. The admittance spectroscopy was measured to explain the different mechanism of reducing hole between organic/organic inorganic/organic MQW
Electroluminescence of doped organic thin films
Electroluminescent (EL)devices are constructed using multilayer organic thin films. The basic structure consists of a hole‐transport layer and a luminescent layer. The hole‐transport layer is an amorphous diamine film in which the only mobile carrier is the hole. The luminescent layer consists of a host material, 8‐hydroxyquinoline aluminum (Alq), which predominantly transports electrons. High radiance has been achieved at an operating voltage of less than 10 V. By doping the Alq layer with highly fluorescent molecules, the EL efficiency has been improved by about a factor of 2 in comparison with the undoped cell. Representative dopants are coumarins and DCMs. The ELquantum efficiency of the doped system is about 2.5%, photon/electron. The EL colors can be readily tuned from the blue‐green to orange‐red by a suitable choice of dopants as well as by changing the concentration of the dopant. In the doped system the electron‐hole recombination and emission zones can be confined to about 50 A near the hole‐transport interface. In the undoped Alq, the EL emission zone is considerably larger due to excitondiffusion. The multilayerdopedEL structure offers a simple means for the direct determination of excitondiffusion length.
SR topography of plastically deformed Fe-Si bicrystals - observation in situ and post mortem
SR reflection topography was applied to study the interaction of slip dislocations with the grain boundaries in Fe-4at%Si bicrystals deformed by compression. Three experimental settings with either a white or monochromatic beam were used and the corresponding orientation contrast analysed. Dislocation transmission through the grain boundary was observed in bicrystals with favourable geometry of the slip systems.