The mechanism of charge generation in charge generation units containing HATCN for high-luminance tandem OLED display

We report the rate limiting step of charge generation in the charge generation units (CGUs) composed of a p-HTL, HATCN and n-doped electron transporting layer (n-ETL) where TAPC was used as the HTL. Energy level alignment determined by the capacitance-voltage (C-V) measurements and the current density-voltage characteristics of the structure clearly showed that the electron injection at the HATCN/n-ETL junction limits the charge generation in the CGUs rather than charge generation itself at the p-HTL/HATCN junction. Consequently, the CGUs with 30 mol% Rb2CO3 doped BPhen formed with the HATCN layer generates charges very efficiently and the excess voltage required to generate the current density of ±10 mA/cm2 was around 0.17 V, which is extremely small compared with the literature values reported up to now.

[1]  Ki-Bum Kim,et al.  Origin of charge generation efficiency of metal oxide p-dopants in organic semiconductors , 2011 .

[2]  Dong-Seok Leem,et al.  Effect of host organic semiconductors on electrical doping , 2010 .

[3]  C. M. Elliott,et al.  Organic homojunction diodes with a high built-in potential: interpretation of the current-voltage characteristics by a generalized Einstein relation. , 2005, Physical review letters.

[4]  Chih-I Wu,et al.  A high performance inverted organic light emitting diode using an electron transporting material with low energy barrier for electron injection , 2011 .

[5]  Ki-Bum Kim,et al.  Homogeneous dispersion of organic p-dopants in an organic semiconductor as an origin of high charge generation efficiency , 2011 .

[6]  Siegfried Karg,et al.  Light-emitting diodes based on poly-p-phenylene-vinylene: II. Impedance spectroscopy , 1997 .

[7]  T. Riedl,et al.  Temperature-independent field-induced charge separation at doped organic/organic interfaces: Experimental modeling of electrical properties , 2007 .

[8]  Jang‐Joo Kim,et al.  The Mechanism of Charge Generation in Charge‐Generation Units Composed of p‐Doped Hole‐Transporting Layer/HATCN/n‐Doped Electron‐Transporting Layers , 2012 .

[9]  Yong-ki Kim,et al.  Energy level alignment at a charge generation interface between 4,4'-bis(N-phenyl-1-naphthylamino)biphenyl and 1,4,5,8,9,11 -hexaazatriphenylene-hexacarbonitrile , 2009 .

[10]  Q. Bao,et al.  Electronic structures of MoO3-based charge generation layer for tandem organic light-emitting diodes , 2010 .