Study On The Phosphorescent Materials Concentration Optimism Of White Organic Light-emitting Diodes

Organic light-emitting diodes has became the new generation display production after liquid crystal display and wide applications prospect in solid state lighting by virtue of light weight,thin thickness,flexible,high brightness,high efficiency,simple processing technology,broad visual angle,wide operating temperature range,spread materials source,can work at low voltage and no need to prepare back light.Over the several decades,study of OLED has derived from fundamental research to the development of product engineering and industrialization.The further improvement of comprehensive performance of OLED is essential for the purpose of meet the requirements of solid state light and flat display.In recent years,performances of organic light-emitting devices have been improved dramatically by developing new material and architectures.Phosphorescent OLEDs are more effective because phosphorescent materials can leads to the potential to achieve 100% internal emission efficiency in principle.In this paper,a double emission layers(D-EMLs)structure was proposed for obtaining white organic light-emitting diodes with high efficiency and low efficiency roll-off.The former EML(near the anode)is MCP doped with Bis(2-methyldibenzo[f,h]quinoxaline)(acetylacetonate)-iridium(III)Ir(MDQ)2(acac)and Tris(2-phenylpyridine)iridium(III)Ir(ppy)3,while the later EML(near the cathode)is MCP doped with Bis(4-phenylthieno[3,2-c]pyridinato-N,C20)acetylacetonate iridium(III)PO-01 and Bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium(III)FIr Pic,and they are separated by a mixed interlayer of MCP: Tm Py Pb.The interlayer of MCP: Tm Py Pb with the ratio of 1:1shows bipolar transport ability,leading to more efficient transport of holes and electrons in both EMLs,which furthur expands the exciton recombination zone on the basis of double-emission layer.A concentration modulation variation of FIr Pic further improves the device performance by redistributing the carriers and restraining the triplet-triplet annihilation.The resulting device with the optimized concentration shows the maximum efficiency of 31.0 cd/A(21.5 lm/W),as well as a reducedefficiency roll-off.