ZnOEP∶Alq_3掺杂体系的电致发光

Electroluminescence from 2,3,7,8,12,13,17,18 octaethyl-21H23H porpine Zinc (ZnOEP) in Tris(8-hydroxyquinoline) Aluminum (Alq_3) Host

采用八乙基卟啉锌 ( 2 ,3 ,7,8,1 2 ,1 3 ,1 7,1 8 octaethyl 2 1H2 3H porphinezinc,ZnOEP)掺杂八羟基喹啉铝为发光层 ,在不同的掺杂浓度下 ,制备了结构为ITO/TPD/ZnOEP∶Alq3 /Alq3 /Mg∶Ag的多个器件 ,并测试了他们的发光光谱、亮度 -电流曲线以及亮度对时间的响应特性。结果发现 ,当ZnOEP掺杂浓度从 0 5%变化到 1 5%时 ,器件的发光光谱明显不同 ,可以分别得到从橙黄色到红色等不同发光颜色的器件 ,器件的发光效率也从 0 96cd/A变化到 0 1 4cd/A。上述现象可由ZnOEP的自吸收和浓度猝灭效应来解释。另外 ,器件的驱动特性表明 ,Alq3 和ZnOEP之间可能存在能量传递过程。

Organic electroluminescent (EL) devices have attracted much attention because of their high potential for full color large area flat panel display applications. One of the important steps for full color displays is the realization of red electroluminescence (EL). Porphyrin compounds have many derivatives that have various molecular structure and electronic states,including PtOEP,TPP,ZnTPP ect.,which were used for red emitting materials.In this paper,a new compound 2,3,7,8,12,13,17,18 octaethyl 21H23H porpine zinc (ZnOEP) was proposed for red electroluminescence. Organic EL devices with ZnOEP as a dopant at various concentrations within a tris (8 hydroxyquinoline) aluminum (Alq 3) host layer were prepared by conventional vapor deposition. The multi layer structure of the devices is ITO/TPD/ZnOEP∶Alq 3/Alq 3/Mg∶Ag.For deposition of the ZnOEP∶Alq 3 layer,the evaporation rates for the ZnOEP dopant and the Alq 3 host were independently controlled by separate thin film deposition monitor.The dopant concentrations in the Alq\-3 were 0 5,2,10 and 15wt%,respectively. EL spectra, B J curves and pulse response characteristics of the devices were measured. It was found that EL spectra and B J curves were significantly different as the dopant concentration varied.In the spectra of all the devices,there were two peaks at about 590nm and 630nm,which were originate from ZnOEP molecular excitons.It is observed that the peak at 590nm becomes weaker when the ZnOEP dopant concentration increases and the emission color turns from orange to red, while the luminance efficiency drops from 0 96cd/A to 0 14cd/A.The experimental results may be explained by the following two factors:the self absorption of ZnOEP and the phenomena of concentrated quenching. Additionally, response time characteristics were obtained by measuring the EL light waveforms while using rectangular voltage pulses of 100μs duration. The pulse response characteristic of the device may indicate the existence of the energy transfer between the Alq 3 and the ZnOEP molecules. In conclusion,it is the first time to get electroluminescence from ZnOEP∶Alq 3 system in this paper.The EL spectra of the devices changed with the ZnOEP dopant concentration due to the self absorption of ZnOEP and the phenomena of concentrated quenching.When the ZnOEP dopant concentration is over 10%,red electroluminescence was obtained.In additional,the pulse response characteristics of the devices were investigated,too.