Performance Enhancement and emission color adjustment of white organic light-emitting diodes with hole-blocking layer

• Main Authors: Bo-Cheng Hong, 洪舶承
• Other Authors: Su-Hua Yang
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/64594449666133916578

碩士 === 國立高雄應用科技大學 === 電子與資訊工程研究所碩士班 === 96 === A high efficiency and luminance of white organic light-emitting diode (WOLED) was successfully fabricated using the structure of ITO/NPB(50 nm)/[TBADN：BCzVB(12 %) (13 nm)/BCP(2 nm)/Alq3：DCJTB(0.2 %) (10 nm)]3 /Alq3(10 nm) /LiF (1 nm)/Al(200 nm). Due to HOMO of TBADN is higher than that of Alq3, an excess of electrons was accumulating in the electron transporting layer. Adding BCP layers between the blue emission layer (BEML) and red emission layer (REML), a better charge balance in the recombination zone and an improved performance could be obtained. BCP is not only used as the hole-blocking layer but also adjusts carrier recombination behavior in the BEML and REML. Before adding BCP layers, the CIE coordinates of the device were x = 0.48, y = 0.36 for the maximum luminance of 30400 cd/m2 at 10 V. The maximum current efficiency were 6.07 cd/A at 6 V. While inserting three BCP layers (1 nm), the CIE coordinates of the device were x = 0.44, y = 0.36 for the maximum luminance of 37700 cd/m2 at 11 V. The maximum current efficiency were 7.6 cd/A at 10 V. When the thickness of BCP layer was 2 nm, the CIE coordinates of the device were x = 0.32, y = 0.32 for the maximum luminance of 33600 cd/m2 at 10 V. The maximum current efficiency were 7.06 cd/A at 10 V. Devices with three (1 nm) BCP layers had the best luminance and efficiency due to applicable hole-blocking; thicker BCP layer might lead to lower carrier recombination. When the optimum thickness of 2 nm of BCP layer was inserted between BEML and REML layer, the device emitted the nearest white light.