# Properties of Polymer Light Emitting Diodes Using PFO : MEH-PPV Emission Layer and Hole Blocking Layer

• Lee, Hak-Min (Department of Electronic and Electrical Engineering, Dankook University) ;
• Gong, Su-Cheol (Department of Electronic and Electrical Engineering, Dankook University) ;
• Shin, Sang-Bae (Department of Electronic and Electrical Engineering, Dankook University) ;
• Park, Hyung-Ho (Department of Ceramics Engineering, Yonsei University) ;
• Jeon, Hyeong-Tag (Division of Materials Science and Engineering, Hanyang University) ;
• Chang, Ho-Jung (Department of Electronic and Electrical Engineering, Dankook University)
• 발행 : 2008.06.30

#### 초록

The yellow base polymer light emitting diodes(PLEDs) with double emission and hole blocking layers were prepared to improve the light efficiency. ITO(indium tin oxide) and PEDOT : PSS[poly(3,4-ethylenedioxythiophene) : poly(styrene sulfolnate)] were used as cathode and hole transport materials. The PFO[poly(9,9-dioctylfluorene)] and MEH-PPV[poly(2-methoxy-5(2-ethylhe xoxy)-1,4-phenylenevinyle)] were used as the light emitting host and guest materials, respectively. TPBI[Tpbi1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene] was used as hole blocking layer. To investigate the optimization of device structure, we prepared four kinds of PLED devices with different structures such as single emission layer(PFO : MEH-PPV), two double emission layer(PFO/PFO : MEH-PPV, PFO : MEH-PPV/PFO) and double emission layer with hole blocking layer(PFO/PFO : MEH-PPV/TPBI). The electrical and optical properties of prepared devices were compared. The prepared PLED showed yellow emission color with CIE color coordinates of x = 0.48, y = 0.48 at the applied voltage of 14V. The maximum luminance and current density were found to be about 3920 cd/$m^2$ and 130 mA/$cm^2$ at 14V, respectively for the PLED device with the structure of ITO/PEDOT : PSS/PFO/PFO : MEH-PPV/TPBI/LiF/Al.