Phosphorescent-sensitized triplet-triplet annihilation in tris(8-hydroxyquinoline) aluminum

We characterized the photoluminescence properties of an amorphous tris(8-hydroxyquinoline) aluminum (Alq3) thin film heavily doped with fac tris(2-phenylpyridine) iridium [Ir(ppy)3] at 8 K. Not only green fluorescence but also red phosphorescence from Alq3 was clearly observed, where Ir(ppy)3 plays the important role as a phosphorescent sensitizer for Alq3. The triplet energy of Alq3 was estimated to be 2.03 eV from the highest energy peak of the phosphorescence spectrum. The fluorescence intensity was proportional to the excitation power. On the other hand, the deviation from the linearity of the phosphorescence intensity to the excitation power was observed above ∼0.01W∕cm2. This nonlinear phosphorescence behavior is well explained by the simple triplet-triplet annihilation theory. It was demonstrated that the efficient triplet energy transfer from Ir(ppy)3 enables us to observe triplet-triplet annihilation in Alq3.

[1]  L. De Cola,et al.  Photochromic dithienylethene derivatives containing Ru(II) or Os(II) metal units. Sensitized photocyclization from a triplet state. , 2004, Inorganic chemistry.

[2]  Yong Qiu,et al.  Blue phosphorescent dye as sensitizer and emitter for white organic light-emitting diodes , 2004 .

[3]  J. Birks,et al.  Delayed excimer fluorescence , 1966 .

[4]  Stephen R. Forrest,et al.  Transient analysis of organic electrophosphorescence: I. Transient analysis of triplet energy transfer , 2000 .

[5]  Yongfang Li,et al.  Highly efficient polymer light-emitting devices using a phosphorescent sensitizer , 2002 .

[6]  C. Gärditz,et al.  The triplet state in tris-(8-hydroxyquinoline)aluminum , 2004 .

[7]  C. Tang,et al.  Organic Electroluminescent Diodes , 1987 .

[8]  M. Fernandes,et al.  Characterization of the triplet state of tris(8-hydroxyquinoline)aluminium(III) in benzene solution. , 2003, Journal of the American Chemical Society.

[9]  M. Cölle,et al.  Thermal, structural and photophysical properties of the organic semiconductor Alq3 , 2004 .

[10]  M. Cölle,et al.  Phosphorescence of aluminum tris(quinoline-8-olate) , 2004 .

[11]  Raymond Kwong,et al.  Triplet exciton confinement and unconfinement by adjacent hole-transport layers , 2004 .

[12]  Stephen R. Forrest,et al.  Transient analysis of organic electrophosphorescence. II. Transient analysis of triplet-triplet annihilation , 2000 .

[13]  R. Ballardini,et al.  Phosphorescent 8-quinolinol metal chelates. Excited-state properties and redox behavior , 1986 .

[14]  I. Chen,et al.  Rapid intersystem crossing in highly phosphorescent iridium complexes , 2004 .

[15]  S. R. Forrest,et al.  High-efficiency fluorescent organic light-emitting devices using a phosphorescent sensitizer , 2000, Nature.

[16]  Feng Li,et al.  White organic light-emitting devices using a phosphorescent sensitizer , 2003 .

[17]  Shizuo Tokito,et al.  Energy-transfer and light-emission mechanism of blue phosphorescent molecules in guest-host systems , 2004 .

[18]  W. Brütting,et al.  A new crystalline phase of the electroluminescent material tris(8-hydroxyquinoline) aluminum exhibiting blueshifted fluorescence , 2001 .

[19]  Richard L. Martin,et al.  Molecular and solid-state properties of tris-(8-hydroxyquinolate)-aluminum , 2000 .