A triple-layer light-emitting diode based on an organic salt ASPT (trans-4-[p-[N-methyl-N-(hydroxyethyl)amino]styryl]-N-methylpyridinium tetraphenylborate), in which TPD and Alq3 were employed as hole and electron transporting materials respectively, exhibits variable electroluminescence (EL) spectra under different applied voltage. At lower voltage, the EL spectrum peaks at 560 nm, which emanates from the TPD/ASPT interface; when the voltage is further increased, the peak at 610 nm, which is originated from ASPT, increases; at higher applied voltage, the device yields green light with a peak at 530 nm and a shoulder at 610 nm. The stronger emission peaking at 530 nm stems from the Alq3. It reveals the hole-electron recombination zone depends on the applied voltage, so the color-variable EL can be observed by adjusting the applied voltage.
© 2005 Chinese Optics Letters
Xueyuan Feng, Jiayu Zhang, Chunxiang Xu, Chang Liu, Guangcai Lv, Zhenning Tang, and Yiping Cui, "Color-tunable triple-layer electroluminescent devices based on organic salt," Chin. Opt. Lett. 3, S293-S294 (2005)