버퍼층으로 사용한 PVK의 농도 변화에 따른 유기 발광 소자의 전압-전류-휘도 특성

Current-Voltage-Luminance Characteristics of Organic Light-Emitting Diodes with a Variation of PVK Concentration Used as a Buffer Layer

We have seen the effects of buffer layer in organic light-emitting diodes(OLEDs) using poly(N-vinylcarbazole)(PVK) depending on a concentration of PVK. Polymer PVK buffer layer was made using spin casting technique. Two device structures were fabricated; one is ITO/TPD/Alq_3/Al as a reference, and the other is ITO/PVK/TPD/Alq_3/Al to see the effects of buffer layer in organic light-emitting diodes. Current-voltage-luminance characteristics and an external quantum efficiency were measured with a variation of spin-casting rpm speeds and PVK concentration. We have obtained an improvement of external quantum efficiency by a factor of four when the PVK concentration is 0.1wt% is used. The improvement of efficiency is expected due to a function of hole-blocking of PVK in OLEDs.