외부발광층을 양자점의 광특성을 이용해 제작한 백색 유기발광소자의 전기적 및 광학적 특성에 관한 연구

Abstract

After an organic light-emitting device (OLED) was fabricated and its performance was demonstrated, the enhancement of the efficiency using functional materials for OLED applications has been extensively investigated. White OLEDs (WOLEDs) have been particularly attractive because of their possible applications in solid-state lighting sources and flat panel display backlights. WOLEDs as lightening sources enjoy their excellent advantages of energy saving, thin film, and flexibility to replace traditional incandescent white light sources. WOLEDs combining blue OLEDs with a color down conversion layer (CCL) have been proposed to simplify the fabrication process and decrease the cost. Commercial white light sources are typically composed of the blue InGaN LED and the yellowish-green yttrium aluminum garnet (YAG) phosphors. White LEDs still encounter the challenges of improving color rendering index (CRI) and correlated color temperature (CCT), in spite of their excellent characteristics such as high efficiency, low power consumption and long lifetime. Some investigations made attempts to compose white LEDs with red quantum dots (QDs) to overcome the poor CRI due to the lack of red component. The QDs with a narrow emission peak can be effectively excited by ultraviolet (UV) or visible light, and the emission peak and intensity can be tuned by their size, species, and band alignment. Even though some studies concerning the electrical and optical properties of the WOLEDs with a CCL utilizing both phosphors and QDs have been performed, very few investigations on the color stabilization of the OLEDs with phosphors and cores-shell QDs embedded in a polymer layer acting as a CCL have been conducted. This paper reports data for color stability of WOLEDs with a CCL utilizing CdSe/ZnS QDs and phosphors dispersed in a polymethylmethacrylate (PMMA) layer.