【作者】 乔泊；

【导师】 徐叙瑢； 赵谡玲；

【作者基本信息】 北京交通大学 ， 材料物理与化学， 2012， 硕士

【摘要】 本论文首先利用改进的化学溶液法制备了ZnO量子点,通过X射线衍射(XRD)、透射电镜(TEM)、原子力显微镜(AFM)、吸收光谱(Abs)、光致发光光谱(PL)等进行表征,证明ZnO量子点粒径均匀(直径约为4.83nm),分散性良好。由于量子效应,Abs和PL与ZnO体材料相比均发生了一定程度的蓝移,Abs吸收边由体材料的370nm蓝移到359nm,PL发光峰由体材料的387nm蓝移到377nm左右,并且粒径越小,蓝移越大。进行了ZnO量子点稳定性研究,通过改变ZnO量子点在乙醇中的浓度调节ZnO量子点在乙醇中分散度,浓度由大到小(从1.6mol/L到0.05mol/L),得到了381nm-375nm不同发光峰的光致发光光谱,这是由分散度不同导致ZnO量子点的团聚所致。PL只有近紫外发光峰,为ZnO量子点的激子态发光,证明ZnO量子点表面缺陷和杂质缺陷较少。另外,研究了ZnO量子点的陈化现象,在不同条件下(25℃陈化30天、0℃冷藏陈化30天和新制备的样品)陈化将对导致团聚和对ZnO量子点材料的形貌及光致发光光谱都有不同的影响,研究了ZnO的团聚机制以及导致团聚的原因。ZnO量子点由于库伦阻塞效应,具有较好的电子传输特性。进行了ZnO量子点作为电子传输层(ETL)平衡有机电致发光器件的载流子,改善MEH-PPV的发光特性。制备了结构为ITO/PEDOT:PSS/MEH-PPV/ZnO QDs/Al和结构为ITO/PEDOT:PSS/MEH-PPV/Al的器件,并进行了对比,ZnO量子点作为电子传输层使发光器件的发光特性以及亮度等得到了很好的改善,启亮电压为3.0V,电压为8V时电流由8mA增加到14mA,光功率由112nw增加到147nw,EL发光峰为MEH-PPV的590nm,峰位未发生移动。根据ZnO量子点的量子蓝移效应,理论上可以得到比ZnO体材料更短波长的近紫外光发射。量子点LED由于其发光材料的窄带宽,发光颜色更纯更饱和(半峰宽一般为40nm),发光峰根据量子点粒径尺寸可调。因此本论文进行了通过ZnnO量子点掺杂的方法使ZnO量子点作为发光层(EL)的尝试,制备了结构为ITO/PEDOT:PSS/MEH-PPV:ZnO QDs/Al和结构为ITO/PEDOT:PSS/MEH-PPV/Al的器件进行了对比,但是最终由于表面悬挂键等表面缺陷导致的淬灭等原因,并未得到ZnO量子点的近紫外光发射。更多还原

【Abstract】 The preparation of ZnO quantum dots (QDs) with modified chemical solution method was studied, and ZnO QDs were characterized with X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Absorption Spectrum (Abs) and Photoluminescence Spectrum (PL) methods. The size of ZnO QDs was uniform (the diameter of ZnO QDs is approximately4.83nm). The ZnO QDs were randomly distributed in the ethyl alcohol; the blue shift of optical absorption edge (from370nm to359nm) and photoluminescence peak (from387nm to approximately377nm) was observed because of a so-called quantum size effect.The stability of ZnO QDs was studied. Different dispersion degree of ZnO QDs distributed in the ethyl alcohol were prepared by changing the density of ZnO QDs (from1.6mol/L to0.05mol/L). Photoluminescence peaks from381nm to371nm were observed, the cause of which was researched. Only nearly ultraviolet photoluminescence peaks were observed, which came from the excitonic luminescence of ZnO QDs, proving that surface defect and impurity defect were less in ZnO QDs. The ageing of ZnO QDs was also studied. Ageing under different conditions (room temperature25℃ageing for30days,0℃ageing for30days and ZnO QDs just prepared), the reunion, topography and PL peaks of ZnO QDs would be different. The reunion mechanism and the cause of it were discussed.ZnO QDs have good electronic transmission characteristics because of their Coulomb blockade effect. Therefore, ZnO QDs applied as Electron Transport Layer (ETL) to balance of the charge carriers in inorganic-organic light-emitting diodes (LEDs) and to improve the luminous efficiency of MEH-PPV was studied. The device started luminising at voltage3.0V,(The current is from8mA to14mA at voltage8.0V; the light power is from112nw to147nw at voltage8.0V); The EL peak is590nm.Theoretically, nearly ultraviolet emission (blue shift compared to that of ZnO bulk materials) could be observed, based on the quantum blue shift effect of ZnO QDs. Quantum-dot-based LEDs are characterized by pure and saturated emission colors (Halfpeak breadth is more or less40nm) with narrow bandwidth, and their emission wavelength is easily tuned by changing the size of the quantum dots. Therefore, we tried to dope ZnO QDs into MEH-PPV as Emitting Layer (EL) in order to get the nearly ultraviolet emission of ZnO QDs, but failed because of quenching, which came from the surface defect (such as dangling bonds on the surface) of ZnO QDs.更多还原