A new structure containing negative refractive index dielectric layer（NRlDL） is introduced into microcavity. The properties of the new mierocavity organic light-emitting devices（MOLEDs） are investigated. In the ex...A new structure containing negative refractive index dielectric layer（NRlDL） is introduced into microcavity. The properties of the new mierocavity organic light-emitting devices（MOLEDs） are investigated. In the experiment, the transfer matrix method is adopted. The dependence of reflectance and transmittance on the refractive index and thickness of NRIDL are analyzed in detail. Compared with the electroluminescence spectra of non-NRIDL diodes, the line widths of the spectra of the MOLEDs are narrower and all the peaks enhance. The results show that the new structure is beneficial to improve the performance and reduce the thickness of microcavity devices.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
A new aqueous chemical growth method for generation of ZnO flowerlike and spindlelike nanostructures, transformed from layered basic zinc acetate （LBZA） nanobelts, is developed. The novel as-synthesized ZnO flowerli...A new aqueous chemical growth method for generation of ZnO flowerlike and spindlelike nanostructures, transformed from layered basic zinc acetate （LBZA） nanobelts, is developed. The novel as-synthesized ZnO flowerlike and spindlelike nanostructures are mainly due to the pH. They are characterized using X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The X-ray diffraction peaks indicate that these ZnO nanostructures prefer to grow along the C-axis. Photoluminescence （PL） measurements show that the ZnO flowerlike nanostructures have strong ultraviolet （UV） emission properties at 380 rim, while no defect-related visible emission can be detected. The good performance for photoluminescence emission makes the ZnO flowerlike nanostructures to be promising candidates for photonic and electronic device applications.展开更多
基金Natural Science Research Item of Education Department of Henan Province(2008A430009)Doctor Foundation of Henan Polytechnic University(B2008-22)
文摘A new structure containing negative refractive index dielectric layer（NRlDL） is introduced into microcavity. The properties of the new mierocavity organic light-emitting devices（MOLEDs） are investigated. In the experiment, the transfer matrix method is adopted. The dependence of reflectance and transmittance on the refractive index and thickness of NRIDL are analyzed in detail. Compared with the electroluminescence spectra of non-NRIDL diodes, the line widths of the spectra of the MOLEDs are narrower and all the peaks enhance. The results show that the new structure is beneficial to improve the performance and reduce the thickness of microcavity devices.
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.
基金supported by the National High Technology Research and Development Program of China (Nos.2007AA030112 and2009AA032708)
文摘A new aqueous chemical growth method for generation of ZnO flowerlike and spindlelike nanostructures, transformed from layered basic zinc acetate （LBZA） nanobelts, is developed. The novel as-synthesized ZnO flowerlike and spindlelike nanostructures are mainly due to the pH. They are characterized using X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The X-ray diffraction peaks indicate that these ZnO nanostructures prefer to grow along the C-axis. Photoluminescence （PL） measurements show that the ZnO flowerlike nanostructures have strong ultraviolet （UV） emission properties at 380 rim, while no defect-related visible emission can be detected. The good performance for photoluminescence emission makes the ZnO flowerlike nanostructures to be promising candidates for photonic and electronic device applications.
