다공성 고분자 발광층을 이용한 백색 유기발광소자의전기적 및 광학적 특성에 대한 연구

Abstract

White organic light-emitting devices (WOLEDs) have attracted considerable interest due to their potential applications of full-color displays and lighting source1-3 due to their advantages of ultrathin, light weight, and low power consumption. High-efficiency WOLEDs with a multiple emitting layer (EML) were suggested due to their simple concept and easy fabrication method. While WOLEDs with a multiple EML have been introduced to obtain higher efficiency and tunable emission spectra, the WOLEDs with multiple EMLs have inherent problems of the poor color stability and the difficulty in color control in spite of the achievement of the high efficiency. An alternative method for the fabrication of WOLEDs is the utilization of a single EML with red, green, and blue color emitting materials. However, because an exciton movement in the single EML significantly depends on the luminance of the device, the emission color control of the WOLEDs with a single EML is difficult to moderate an emitting color. The WOLEDs with an EML consisting of the separated red, green and blue emitting regions effectively change the exciton recombination zone, resulting in an improvement of the color stability of WOLEDs. Even though studies on hybrid small molecule/polymer WOLDs with a separated EML have been performed, investigations about effects of the polymer blending ratio on the tunable color of WOLEDs with a hybrid small molecule/polymer EML have not been reported yet. This paper reports the effects of the polymer blending ratio on the tunable color of WOLEDs with a hybrid small molecule/polymer EML. Atomic force microscopy measurements were performed to investigate the surface morphologies of the blending polymer films and the porous films. Current density-voltage, luminance-voltage, and electroluminescence (EL) measurements for the WOLEDs with a hybrid small molecule/polymer EML fabricated utilizing various polymer blending ratios were carried out to investigate their electrical and optical properties.