596
S. Yagi
Another type of TADF emitter is based on HOMO–LUMO separation by the multiple
resonance effect. The ICT-type TADF emitters show PL and EL spectra with relatively large half bandwidths due to structural relaxation upon excitation. On the other
hand, the structural relaxation is considerably suppressed in TADF emitters with the
multiple resonance effect, and thus quite narrow half bandwidths of ca. 20 nm or less
are achieved. It is noteworthy that pure blue OELDs with η ext s almost reaching the
theoretical limit have been developed using this type of TADF emitters.
In near future, OLEDs will be increasingly required to develop flat panel displays,
illumination apparatuses, electronic papers, and other display devices. Toward
widespread of OLEDs as smart devices, the device performance should be further
improved. It is undoubted that emitting materials play an important role in the next
breakthrough of the OLED technology.
References
Adachi C, Tsutsui T, Saito S (1990) Confinement of charge carriers and molecular excitons within
5-nm-thick emitter layer in organic electroluminescent devices with a double heterostructure.
Appl Phys Lett 57:531–533
Adachi C, Baldo MA, Thompson ME, Forrest SR (2001a) Nearly 100% internal phosphorescence
efficiency in an organic light-emitting device. J Appl Phys 90:5048–5051
Adachi C, Kwong RC, Djurovich P, Adamovich V, Baldo MA, Thompson ME, Forrest SR
(2001b) Endothermic energy transfer: a mechanism for generating very efficient high-energy
phosphorescent emission in organic materials 79:2082–2084
(a) Adamovich V,Brooks J, Tamayo A, Alexander AM, Djurovich PI, D’Andrade BW, Adachi
C, Forrest SR, Thompson ME (2002) High efficiency single dopant white electrophosphorescent light emitting diodes. New J Chem 26:1171–1178; (b) Kim D, Brédas JL (2009) Triplet
excimer formation in platinum-based phosphors: a theoretical study of the roles of Pt-Pt bimetallic
interactions and interligand π–π interactions. J Am Chem Soc 131:11371–11380; (c) Shigehiro
T, Yagi S, Maeda T, Nakazumi H, Fujiwara H, Sakurai Y (2013) Photo- and electroluminescence from 2-(Dibenzo[b,d]furan-4-yl)pyridine-based heteroleptic cyclometalated platinum(II)
complexes: excimer formation drastically facilitated by an aromatic diketonate ancillary ligand.
J Phys Chem C117:532–542; (d) Shigehiro T, Chen Q, Yagi S, Maeda T, Nakazumi H, Sakurai Y
(2016) Substituent effect on photo- and electroluminescence properties of heteroleptic cyclometalated platinum(II) complexes based on a 2-(Dibenzo[b,d]furan-4-yl)pyridine ligand. Dyes Pigm
124:165–173; (e) Okamura N, Maeda T, Fujiwara H, Soman A, Unni KNN, Ajayaghosh A, Yagi S
(2018) Photokinetic study on remarkable excimer phosphorescence from heteroleptic cyclometalated platinum(II) complexes bearing a benzoylated 2-phenylpyridinate ligand. Phys Chem Chem
Phys 20:542–552
Auer-Berger M, Trattnig R, Qin T, Schlesinger R, Nardi MV, Ligorio G, Christodoulou C, Koch
N, Baumgarten M, Müllen K, List-Kratochvil EJW (2016) All-solution-processed multilayer
polymer/dendrimer light emitting diodes. Org Electron 35:164–170
Bolink HJ, Barea E, Costa RD, Coronado E, Sudhakar S, Zhen C, Sellinger A (2008) Efficient
blue emitting organic light emitting diodes based on fluorescent solution processable cyclic
phosphazenes. Org Electron 9:155–163
(a) Caspar JV, Kober EM, Sullivan BP, Meyer TJ (1982) Application of the energy gap low to the
decay of charge-transfer excited states. J Am Chem Soc 104:630–632; (b) Sommer JR, Shelton
AH, Parthasarathy A, Ghiviriga I, Reynords JR, Schanze KS (2011) Photophysical properties of
near-infrared phosphorescent π-extended platinum porphyrins. Chem Mater 23:5296–5304
S. Yagi
Another type of TADF emitter is based on HOMO–LUMO separation by the multiple
resonance effect. The ICT-type TADF emitters show PL and EL spectra with relatively large half bandwidths due to structural relaxation upon excitation. On the other
hand, the structural relaxation is considerably suppressed in TADF emitters with the
multiple resonance effect, and thus quite narrow half bandwidths of ca. 20 nm or less
are achieved. It is noteworthy that pure blue OELDs with η ext s almost reaching the
theoretical limit have been developed using this type of TADF emitters.
In near future, OLEDs will be increasingly required to develop flat panel displays,
illumination apparatuses, electronic papers, and other display devices. Toward
widespread of OLEDs as smart devices, the device performance should be further
improved. It is undoubted that emitting materials play an important role in the next
breakthrough of the OLED technology.
References
Adachi C, Tsutsui T, Saito S (1990) Confinement of charge carriers and molecular excitons within
5-nm-thick emitter layer in organic electroluminescent devices with a double heterostructure.
Appl Phys Lett 57:531–533
Adachi C, Baldo MA, Thompson ME, Forrest SR (2001a) Nearly 100% internal phosphorescence
efficiency in an organic light-emitting device. J Appl Phys 90:5048–5051
Adachi C, Kwong RC, Djurovich P, Adamovich V, Baldo MA, Thompson ME, Forrest SR
(2001b) Endothermic energy transfer: a mechanism for generating very efficient high-energy
phosphorescent emission in organic materials 79:2082–2084
(a) Adamovich V,Brooks J, Tamayo A, Alexander AM, Djurovich PI, D’Andrade BW, Adachi
C, Forrest SR, Thompson ME (2002) High efficiency single dopant white electrophosphorescent light emitting diodes. New J Chem 26:1171–1178; (b) Kim D, Brédas JL (2009) Triplet
excimer formation in platinum-based phosphors: a theoretical study of the roles of Pt-Pt bimetallic
interactions and interligand π–π interactions. J Am Chem Soc 131:11371–11380; (c) Shigehiro
T, Yagi S, Maeda T, Nakazumi H, Fujiwara H, Sakurai Y (2013) Photo- and electroluminescence from 2-(Dibenzo[b,d]furan-4-yl)pyridine-based heteroleptic cyclometalated platinum(II)
complexes: excimer formation drastically facilitated by an aromatic diketonate ancillary ligand.
J Phys Chem C117:532–542; (d) Shigehiro T, Chen Q, Yagi S, Maeda T, Nakazumi H, Sakurai Y
(2016) Substituent effect on photo- and electroluminescence properties of heteroleptic cyclometalated platinum(II) complexes based on a 2-(Dibenzo[b,d]furan-4-yl)pyridine ligand. Dyes Pigm
124:165–173; (e) Okamura N, Maeda T, Fujiwara H, Soman A, Unni KNN, Ajayaghosh A, Yagi S
(2018) Photokinetic study on remarkable excimer phosphorescence from heteroleptic cyclometalated platinum(II) complexes bearing a benzoylated 2-phenylpyridinate ligand. Phys Chem Chem
Phys 20:542–552
Auer-Berger M, Trattnig R, Qin T, Schlesinger R, Nardi MV, Ligorio G, Christodoulou C, Koch
N, Baumgarten M, Müllen K, List-Kratochvil EJW (2016) All-solution-processed multilayer
polymer/dendrimer light emitting diodes. Org Electron 35:164–170
Bolink HJ, Barea E, Costa RD, Coronado E, Sudhakar S, Zhen C, Sellinger A (2008) Efficient
blue emitting organic light emitting diodes based on fluorescent solution processable cyclic
phosphazenes. Org Electron 9:155–163
(a) Caspar JV, Kober EM, Sullivan BP, Meyer TJ (1982) Application of the energy gap low to the
decay of charge-transfer excited states. J Am Chem Soc 104:630–632; (b) Sommer JR, Shelton
AH, Parthasarathy A, Ghiviriga I, Reynords JR, Schanze KS (2011) Photophysical properties of
near-infrared phosphorescent π-extended platinum porphyrins. Chem Mater 23:5296–5304