An iridium （Ⅲ） bis[（4,6-difluorophenyl）pyridinato-N, C^2][6-（6＇-（4＂-（ 5＂-phenyl- 1＂, 3＂, 4＂-oxadiazole-2＂-yl） phenoxy） hexyloxy picolinate） was synthesized and characterized by IH NMR and elementary ...An iridium （Ⅲ） bis[（4,6-difluorophenyl）pyridinato-N, C^2][6-（6＇-（4＂-（ 5＂-phenyl- 1＂, 3＂, 4＂-oxadiazole-2＂-yl） phenoxy） hexyloxy picolinate） was synthesized and characterized by IH NMR and elementary analysis in order to study the effect of ancillary ligand of the oxadiazole-based picolinic acid derivative on optophysical properties of its iridium complex, and further to obtain an iridium complex with highly-efficient blue emission. The thermal stability, UV absorption and photoluminescent properties of this iridium complex were investigated. Compared with iridium （Ⅲ） bis[（4,6-difluorophenyl）pyridinato-N, C^2]（picolinate） reported as a highly-efficient blue electroluminescent material, this iridium complex bearing an oxadiazole-based picolinic acid derivative presents higher thermal stability, more intense UV absorption at 291 nm and similar photoluminescent spectrum peaked at 469 nm. This indicates that tuning ancillary ligand of picolinic acid with an oxadiazole unit can improve the optophysical properties of its iridium complex.展开更多
Organic light-emitting diodes （OLEDs） have been extensively studied since the first efficient device based on small molecular luminescent materials was reported by Tang. Organic electroluminescent material, one of t...Organic light-emitting diodes （OLEDs） have been extensively studied since the first efficient device based on small molecular luminescent materials was reported by Tang. Organic electroluminescent material, one of the centerpieces of OLEDs, has been the focus of studies by many material scientists. To obtain high luminosity and to keep material costs low, a few remarkable design concepts have been developed. Aggregation-induced emission （AIE） materials were invented to overcome the common fluorescence-quenching problem, and cross-dipole stacking of fluorescent molecules was shown to be an effective method to get high solid-state luminescence. To exceed the limit of internal quantum efficiency of conventional fluorescent materials, phosphorescent materials were successfully applied in highly efficient electroluminescent devices. Most recently, delayed flu- orescent materials via reverse-intersystem crossing （RISC） from triplet to singlet and the ＂hot exciton＂ materials based on hy- bridized local and charge-transfer （HLCT） states were developed to he a new generation of low-cost luminescent materials as efficient as phosphorescent materials. In terms of the device-fabrication process, solution-processible small molecular lumi- nescent materials possess the advantages of high purity （vs. polymers） and low procession cost （vs. vacuum deposition）, which are garnering them increasing attention. Herein, we review the progress of the development of small-molecule luminescent materials with different design concepts and features, and also briefly examine future development tendencies of luminescent materials.展开更多
Exciton(or spin)statistics is a physical principle based on the statistics of spin multiplicity.In electroluminescence,injected electrons and holes have randomized spin states,and usually form singlet or triplet excit...Exciton(or spin)statistics is a physical principle based on the statistics of spin multiplicity.In electroluminescence,injected electrons and holes have randomized spin states,and usually form singlet or triplet excitons in the ratio of 1:3.Exciton statistics determines that the upper limit of internal quantum efficiency is 25%in fluorescent devices,since only singlet exciton can decay radiatively.However,both experimental and theoretical evidence indicate that the actual efficiency can exceed the exciton statistics limit of 25%by utilizing materials with special electronic structure and optimized device structures.These results bring light to break through the exciton statistics limit and develop new-generation fluorescent materials with low cost and high efficiency.Recently,the exciton statistics,which has attracted great attention in the past decade,is being rejuvenated due to the discovery of some fluorescent materials with abnormally high efficiencies.In view of their significance in theoretical research of organic semiconductors and developing new-generation OLED materials,such materials are widely investigated in both academic institutions and industry.Several key issues still require further clarification for this kind of materials,such as the molecular design concepts.Herein,we review the progress of the materials with efficiency exceeding the exciton statistics limit,and the routes to improve exciton utilization efficiency.In the end,we present an innovative pathway to fully harvest the excitons in fluorescent devices,namely,"hot exciton"model and relevant fluorescence material with hybridized local and charge-transfer(HLCT)excited state.展开更多
基金Projects(20772101,50473046) supported by the National Natural Science Foundation of ChinaProject(2007FJ3017) supported by the Hunan Provincial Science Foundation, ChinaProject(07C764) supported by the Science Foundation of the Education Department of Hunan Province,China
文摘An iridium （Ⅲ） bis[（4,6-difluorophenyl）pyridinato-N, C^2][6-（6＇-（4＂-（ 5＂-phenyl- 1＂, 3＂, 4＂-oxadiazole-2＂-yl） phenoxy） hexyloxy picolinate） was synthesized and characterized by IH NMR and elementary analysis in order to study the effect of ancillary ligand of the oxadiazole-based picolinic acid derivative on optophysical properties of its iridium complex, and further to obtain an iridium complex with highly-efficient blue emission. The thermal stability, UV absorption and photoluminescent properties of this iridium complex were investigated. Compared with iridium （Ⅲ） bis[（4,6-difluorophenyl）pyridinato-N, C^2]（picolinate） reported as a highly-efficient blue electroluminescent material, this iridium complex bearing an oxadiazole-based picolinic acid derivative presents higher thermal stability, more intense UV absorption at 291 nm and similar photoluminescent spectrum peaked at 469 nm. This indicates that tuning ancillary ligand of picolinic acid with an oxadiazole unit can improve the optophysical properties of its iridium complex.
基金supported by the National Natural Science Foundation of China(21334002,51303057,51373054,91233113)the National Basic Research Program of China(2013CB834705,2014CB643504,2015CB655003)+1 种基金the Fundamental Research Funds for the Central Universities(2013ZZ0001)the Introduced Innovative R&D Team of Guangdong(201101C0105067115)
文摘Organic light-emitting diodes （OLEDs） have been extensively studied since the first efficient device based on small molecular luminescent materials was reported by Tang. Organic electroluminescent material, one of the centerpieces of OLEDs, has been the focus of studies by many material scientists. To obtain high luminosity and to keep material costs low, a few remarkable design concepts have been developed. Aggregation-induced emission （AIE） materials were invented to overcome the common fluorescence-quenching problem, and cross-dipole stacking of fluorescent molecules was shown to be an effective method to get high solid-state luminescence. To exceed the limit of internal quantum efficiency of conventional fluorescent materials, phosphorescent materials were successfully applied in highly efficient electroluminescent devices. Most recently, delayed flu- orescent materials via reverse-intersystem crossing （RISC） from triplet to singlet and the ＂hot exciton＂ materials based on hy- bridized local and charge-transfer （HLCT） states were developed to he a new generation of low-cost luminescent materials as efficient as phosphorescent materials. In terms of the device-fabrication process, solution-processible small molecular lumi- nescent materials possess the advantages of high purity （vs. polymers） and low procession cost （vs. vacuum deposition）, which are garnering them increasing attention. Herein, we review the progress of the development of small-molecule luminescent materials with different design concepts and features, and also briefly examine future development tendencies of luminescent materials.
基金financially supported by the National Science Foundation of China(51073069,51273078)the National Basic Research Program of China(2013CB834801)
文摘Exciton(or spin)statistics is a physical principle based on the statistics of spin multiplicity.In electroluminescence,injected electrons and holes have randomized spin states,and usually form singlet or triplet excitons in the ratio of 1:3.Exciton statistics determines that the upper limit of internal quantum efficiency is 25%in fluorescent devices,since only singlet exciton can decay radiatively.However,both experimental and theoretical evidence indicate that the actual efficiency can exceed the exciton statistics limit of 25%by utilizing materials with special electronic structure and optimized device structures.These results bring light to break through the exciton statistics limit and develop new-generation fluorescent materials with low cost and high efficiency.Recently,the exciton statistics,which has attracted great attention in the past decade,is being rejuvenated due to the discovery of some fluorescent materials with abnormally high efficiencies.In view of their significance in theoretical research of organic semiconductors and developing new-generation OLED materials,such materials are widely investigated in both academic institutions and industry.Several key issues still require further clarification for this kind of materials,such as the molecular design concepts.Herein,we review the progress of the materials with efficiency exceeding the exciton statistics limit,and the routes to improve exciton utilization efficiency.In the end,we present an innovative pathway to fully harvest the excitons in fluorescent devices,namely,"hot exciton"model and relevant fluorescence material with hybridized local and charge-transfer(HLCT)excited state.
