CdSe Quantum Dots Luminescence Devices With Organic/Inorganic Composite Structure

CdSe semiconductor quantum dots (QDs) are nanoscale quasi-zero-dimensional materials and have a size effect. CdSe QDs have good light-emitting properties. They are usually used as an inorganic light emitting material in the electroluminescent light emitting devices. Using the size effect in QDs, we can tune emission wavelength of the emitters through changing the size of the QDs. The wavelength of the light emitting from QDs may cover a wide spectral range from blue to the red.In the organic/inorganic composite light emitting device, the active layer is an inorganic semiconductor CdSe QDs. The emission peak of the CdSe QDs used here is580nm with orange color. The defect related emission peak is not observable. the size of The QDs is3.8nm. I studied the electroluminescent properties of the organic/inorganiccomposite electroluminescence device ITO/TPD/CdSe/ZnS/Ag. It has different luminescence phenomenon with the device structure of ITO/ZnS/CdSe/ZnS/Ag. The luminescence intensity is10times of the ITO/ZnS/CdSe/ZnS/Ag structure. As electrons pass through the ZnS acceleration layer, they can excite electrons in CdSe QDs layer by collision and the excited electrons can emit photons. On the other hand the holes injecting into QDs from the TPD layer can recombine with electrons in the QDs layer with emission of photons. Thus there are two light-emitting mechanisms in this device which improves luminescence efficiency. Furthermore, by changing the thickness of the ZnS layer, we found that the band edge emission peak shifts with the variation of thickness, i.e. as thickness of the ZnS layer decreases, the peak position blue-shifts and the peak intensity becomes weak.