发光层厚度对基于CdSSe/ZnS量子点LED性能的影响

Influence of Light Emitting Layer Thickness on the Performance of Quantum Dots LED Based on CdSSe/ZnS Quantum Dots

采用粒径约为10nm的CdSSe/ZnS量子点层作为发光层,制备了叠层结构的量子点发光器件,研究了量子点层厚度对其薄膜形貌及量子点发光二极管性能的影响。原子力显微镜测试结果表明:量子点层过厚时,量子点颗粒发生团聚,且随着厚度的降低,团聚现象减弱;当量子点层厚度和量子点粒径相当时(约为10nm),量子点呈单层排列且团聚现象基本消失;而量子点层厚度低于10nm时,薄膜出现孔洞缺陷。器件的电流-电压-亮度等测试结果表明:量子点发光二极管中量子点层厚度与器件的光电特性密切相关,量子点层厚度为10nm的器件光电性能最优,具有最低的启亮电压4.2V,最高的亮度446cd/m^2及最高的电流效率0.2cd/A。这种通过控制旋涂转速改变量子点层厚度的方法操作简单、重复性好,对QD-LED的研究具有一定应用价值。

In this paper, the laminated structure of quantum dot （QD） light emitting devices were made by using CdSSe/ZnS quantum dots with diameter of about 10 nm as the light emitting layer. The influence of the quantum dot layer thickness on the film morphology and the performance of the quantum dot light emitting diodes was investigated. Atomic force microscopy （AFM） results showed that the quantum dots were agglomerated when the quantum dot layer was too thick, and the aggregation phenomenon was weakened with the decrease of thickness. When the quantum dot layer thickness and quantum dot size were equivalent （about 10 nm）, the quantum dots were arranged in a single layer and the aggregation phenomenon disappeared. When the thickness of the quantum dot layer was below 10 nm, the film was defective with holes. The experimental results showed that the thickness of quantum dot layer in QD LED was closely related to the photoelectric properties of the devices. The optoelectronic properties of the device with the quantum dot layer thickness of 10 nm were the best. It had the lowest light-up voltage of 4.2 V, the highest brightness of 446 cd/m^2 and the highest current efficiency of 0.2 cd/A. The method of changing the thickness of the quantum dot layer by controlling spin speed was simple and reproducible, and had a certain application value to QD-LED research.