Application of ultra-thin CdS film as buffer layer in non-doped blue organic light-emitting diodes
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The device inserted 0.5 nm thick cadmium sulfide (CdS) as buffer layer, prepared by vacuum thermal evaporation method, has been studied on the non-doped blue organic light-emitting diode. Compared to the device without ultra-thin CdS film, the maximum luminance of the device with ultra-thin CdS film was 11,370 cd/m2 at 11 V, and the maximum current efficiency reached 3.10 cd/A, increased 1.5 times and 1.2 times, respectively. In the optimized devices with the structure of ITO/MoO3 (10 nm)/TPABBI (35 nm)/Bphen (40 nm)/CdS (0, 0.1, 0.3 and 0.5 nm)/LiF (0.5 nm)/Al (100 nm), the effects of CdS layer on the photoelectric performance of the devices were investigated in detail. When the CdS thickness was 0.3 nm, the maximum luminance was 13,590 cd/m2 at 9 V and the turn on voltage was only 3 V. The maximum current efficiency of 3.42 cd/A was obtained. It is indicated that the simple structure of the device with inserted ultra-thin CdS film, cheap and stable inorganic photoelectric material, may be a promising way to fabricate hybrid organic–inorganic LEDs with high performances.
KeywordsLower Unoccupied Molecular Orbital Lower Unoccupied Molecular Orbital External Quantum Efficiency Maximum Luminance Electron Transport Layer
Thanks are due to Dr. Ouyang for assistance with emitting materials. This work is supported by the science and technology development program of Jilin province (20100510, 20101512, 201215221), the “Twelfth five-year” science and technology research project of Jilin province department of education (2011321, 2012175, 2013208), the ordinary university graduate student research innovation project of Jiangsu province (CXLX11_0568).