Efficient organic light-emitting diodes using hole-injection buffer layer

• Published in: Journal of Information Display Vol. 4; no. 1; pp. 29 - 33
• Main Authors: Chung, Dong Hoe, Kim, Sang Keol, Lee, Joon Yng, Hong, Jin Woong, Cho, Hyun Nam, Kim, Young Sik, Kim, Tae Wan
• Format: Journal Article
• Language: English; Korean
• Published: Taylor & Francis Group 01.01.2003
• Subjects: buffer layer; efficiency; organic light-emitting diodes; efficiency; organic light-emitting diodes; buffer layer
• ISSN: 1598-0316; 2158-1606
• DOI: 10.1080/15980316.2003.9651910

We have investigated the effects of hole-injection buffer layer in organic light-emitting diodes using copper phthalocyanine (CuPc), poly(vinylcarbazole)(PVK), and Poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) in a device structure of ITO/buffer/TPD/Alq 3 /Al. Polymer PVK and PEDOT:PSS buffer layer were produced using the spin casting method where as the CuPc layer was produced using thermal evaporation. Current-voltage characteristics, luminance-voltage characteristics and efficiency of device were measured at room temperature at various a thickness of the buffer layer. We observed an improvement in the external quantum efficiency by a factor of two, four, and two and half when the CuPc, PVK, and PEDOT:PSS buffer layer were used, respectively. The enhancement of the efficiency is assumed to be attributed to the improved balance of holes and elelctrons resulting from the use of hole-injection buffer layer. The CuPc and PEDOT:PSS layer function as a hole-injection supporter and the PVK layer as a hole-blocking one.