有机多层量子阱结构的发光特性研究

【作者】 赵德威；

【导师】 徐叙瑢；

【作者基本信息】 北京交通大学 ， 光学工程， 2007， 硕士

【摘要】 1987年,C.W. Tang研制成功了亮度大、效率高、驱动电压低的双层电致发光器件,这一突破性进展使得有机电致发光的研究得以在世界范围内迅速而且深入地开展起来。1989年Forrest等人最早提出了有机多层量子阱结构的概念,其具有高的发射效率、窄谱带发射、可调节发射区域和有效地提高载流子平衡等特性,但还有些基本问题有待解决。本文对有机多层量子阱结构的一些基本问题进行了讨论,利用小角X射线衍射对器件结构进行表征,结合常规的光电测量方法,研究了具有量子阱结构作为传输层的有机电致发光器件,以及光致发光中能量传递和蓝移现象,并得到了一些有意义的研究结果:1.小角X射线衍射结果说明制备的器件具有较好的层状结构。2.利用NPB和CBP交替构成量子阱结构作为空穴传输层制备了有机电致发光器件。NPB为空穴的势阱,CBP为空穴的势垒。与常规器件相比,我们得到了发光特性增强的有机电致发光器件。2-周期的器件可达到最大的亮度和发光效率。结果表明,CBP势垒层可以有效地阻挡空穴的传输,降低其达到发光区的数量,进而增强了空穴和电子的平衡。3.与双层结构相比,有机量子阱的多层结构有助于层与层之间的能量传递。比较不同周期的PBD/Alq₃量子阱结构,得到了获得最大能量传递效率的最佳周期数为3。比较不同材料构成的量子阱结构,得到了PBD/Alq₃和BCP/ Alq₃量子阱结构可以实现PBD、BCP向Alq₃能量完全转移,而NPB/Alq₃量子阱结构,NPB和Alq₃之间只是部分能量转移。由于有机量子阱两种材料之间的能量转移是Forster能量转移,那么影响它们之间能量转移的主要因素是给体分子的荧光光谱与受体分子的吸收光谱之间的交叠程度。4.不同Alq₃厚度的PBD/Alq₃双层结构和PBD/Alq₃/PBD量子阱结构的光致发光光谱随着势阱层厚度的降低,都可以引起Alq₃发光峰的蓝移,说明发光峰的蓝移并不是由量子阱结构直接引起的,可能是PBD发光峰的存在,使得PBD与Alq₃的发光峰叠加所引起的。另外,我们还利用BCP/Alq₃和CBP/Alq₃制备成样品,进一步地证明了上述可能的原因。更多还原

【Abstract】 In 1987, C.W. Tang reported the double-layer electroluminescent diode with high brightness, efficiency and low driven voltage. This breakthrough made the research of organic electroluminescent diodes （OLEDs） spread widely through the world, which has developed deeply since then. In 1989, Forrest et al first brought forward the conception of organic multilayer quantum well structure （OMQWs）, which has the characteristics of high emission efficiency, narrowed emission band, tunable emission region and enhanced carriers balance, however, some essential problems still need to be solvedAiming to discuss these basic problems of OMQWs, we study OLEDs with quantum well structures as transporting layer, the energy transfer and blue shift in the photoluminescence （PL） by the use of small angle XRD and conventional opto-electronic measurement techniques and then get some significant results.1. Small angle XRD spectra show that the samples prepared have good layer structure.2. We fabricated the devices with OMQWs, which consisted of alternative NPB and CBP and acted as hole-transporting layer. NPB acts as potential well for the holes and CBP does as potential barrier. Compared with conventional devices, the enhanced luminescent properties of OLEDs are obtained. The device with 2-period quantum well got the maximum brightness and efficiency. The results demonstrate that CBP potential barriers effectively block the holes transportation, reduce the number of carriers arriving at the luminescent region and further enhance the balance of holes and electrons.3. Compared to the double-layer, the OMQWs conduce to the energy transfer from barrier layers to well layers. For the PBD/Alq₃ OMQWs with different periods, the optimum period number is 3 at the maximum energy transfer rate. For the OMQWs with different materials, it can be obtained that the energy from PBD and BCP transfer completely to Alq₃ in PBD/Alq₃ and BCP/ Alq₃ quantum well structures, respectively. However, in NPB/ Alq₃ quantum well structure, the energy from NPB transfers partly to the Alq₃. Because the energy transfer between two materials in OMQWs is Forster energy transfer, the energy transfer is mainly dependent on the overlap between the PL spectra of donor molecule and the absorption spectra of acceptor molecule.4. In the PBD/Alq₃ double-layer and PBD/Alq₃/PBD quantum well structures with different Alq₃ layer thickness, there exists blue shift of Alq₃ emission peak in both of such PL spectra as the thickness of potential well layer is decreased. It indicates that the更多还原