Preparation Of ZnO Quantum Dots By Sol-gel Method And Their Applications In Light-emitting Devices

ZnO as a direct wide band gap?3.37 eV?semiconductor material has high exciton binding energy of 60 meV at room temperature,which is one of alternative representation after GaN for the three generation of semiconductor.Its excellent electron transport and optical properties lead to forming a very promising candidate for LEDs.Compared with other structures of ZnO materials,ZnO quantum dots?QDs?,which own advantages of relatively mature synthesis technology,tunable luminescence wavelength and high quantum yield,possess much potential application in many fields.And the emission wavelength of ZnO QDs is dependent not only on the QDs sizes,but also on the types and numbers of crystal defects.By changing the synthesis conditions,the stable size-controlled ZnO QDs with good optical property are obtained,at the same time the continuous adjustable luminescence wavelength in ultraviolet?UV?and visible regions are also observed.This paper focuses on the design and development of UV and white LEDs based on ZnO QDs.Through optimizing the preparation conditions of ZnO QDs,the improved light-emitting efficiency and tunable luminescence wavelength in the corresponding light-emitting device are achieved.The main research content is as follows:ZnO QDs were fabricated via a sol-gel method.By modulating reaction time,synthesis temperature and reagent concentration,specific preparation conditions on the influence of luminescence wavelength and optical properties in ZnO QDs were studied in detail.Based on the above,in order to enhance UV light-emitting efficiency of ZnO QDs,as a surface plasmon,which can be improved luminescence efficiency,carbon dots?CDs?material were introduced into the LEDs.The UV photoluminescence of ZnO QDs shows a great enhancement after introducing the CDs.In order to comparative study,we construct two devices of ZnO QDs/Al₂O₃/p-GaN and ZnO QDs@CDs/Al₂O₃/p-GaN.It is found that the UV electroluminescence efficiency of LED is observed to be greatly improved after the introduction of the CDs.On the other hand,ZnO QDs can be emitted relatively strong yellow light through regulating its sizes.Using this character,two light-emitting devices of ZnO QDs/p-GaN and ZnO QDs/Al₂O₃/p-GaN were constructed.This research showed that the recombination probability of the carriers of ZnO QDs was increased after embeddedAl₂O₃ electron blocking layer.Therefore,the white emission including the blue light in p-GaN and yellow light in ZnO QDs was achieved.