CBP/Alq3有机量子阱结构的光致发光

采用多源有机分子气相沉积系统(OMBD)制备了CBP/Alq₃有机多量子阱结构,利用电化学循环伏安特性和吸收光谱、小角X射线衍射、荧光光谱研究了量子阱的能带、结构和光致发光的特性。电化学循环伏安特性和吸收光谱的测量结果表明,CBP的最低占据分子轨道(LUMO)与最高占据分子轨道(HOMO)的位置分别为-2.74,-6.00eV,Alq₃的LUMO与HOMO的位置分别为-3.10,-5.80eV,所以CBP/Alq₃有机量子阱为Ⅰ型量子阱结构。小角X衍射测量显示,在小角的位置(2θ的范围在0°～3°)观察到了对应于量子阱结构的多级布拉格衍射峰,表明多层量子阱结构是有序的层状结构,界面比较完整,界面质量比较好。荧光光谱的研究结果表明,Ⅰ型量子阱结构可以有效地把能量从垒层传递给阱层,从而增强了阱层材料的发光。阱层的厚度对发光峰的位置影响很大,随阱层厚度减小,阱层材料的发光峰出现蓝移现象。并对引起发光峰蓝移的原因进行了讨论。

Photoluminescence of 4,4′-N,N′-dicarbazole-biphenyl/8-hydroxyqunoline Aluminum Organic Quantum Well

Inorganic semiconductor multiple quantum well structures have been a subject of intense study due to their interesting electronic and optical properties which have many promising applications in optoelectronic device technology.In the past decade,following organic semiconductor research,organic semiconductor multiple quantum well structures have been studied by many research groups.Organic crystals are bonded by relatively weak Van der Waals forces.Therefore,the potential exists for fabrication of high quality heterostructures or multilayer structures without inducing large strains using a variety of organic crystalline materials.In this paper,quantum well structures consisting of alternating layers of organic 4,4’-N,N’-dicarbazole-biphenyl (CBP)/8-hydroxyqunoline aluminum (Alq₃) have been grown by organic molecular beam deposition.Energy level,structure and optical property of the quantum well are determined by cyclic voltammetry,optical absorption,small angle X-ray diffraction and photoluminescence.Cyclic voltammetry and optical absorption results indicate that the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) levels of CBPare-2.74 and-6.00 eV,and those of Alq₃ are-3.10 and-5.80 eV,respectively.It is clear that the CBP/Alq₃ multilayers possess the energy lineup which can be classified as Type-Ⅰ,where the HOMO of Alq₃ is higher than that of CBPand the LUMO of Alq₃ is lower than that of CBP.The quantum well structure exhibits clear high-order Bragg peaks by small angle X-ray diffraction measurements and this indicates the structure of the quantum well is precisely ordered.The PLexperimental results indicate that the structures of CBP/Alq₃,possessing a Type-Ⅰ energy lineup,exhibit the rapid energy transfer from CBP to Alq₃,and lead to the increase of Alq₃ PLintensity.The PLpeaks of Alq₃ shift to higher energy as the Alq₃ layer thickness is decreased.The origin of the peak emission energy blue shift is discussed with the theoretical and experimental results published in the literatures.