Study On Liquid-type All-inorganic Perovskite Quantum Dot Light-emitting Diode

In recent years,all-inorganic cesium lead halide perovskite?Cs Pb X₃,X = Cl,Br,I or mixed halide elemental of Cl/Br and Br/I?quantum dots?QDs?have been received great attention and application becaused of their outstanding emission properties,such as the high photoluminescence?PL?quantum yield?QY?up to 90%,narrow emission full width at half-maximum?FWHM??12-42 nm?,and tunable emission color?400-750nm?.The synthesis method tends to be diversified,either by using the traditional form of thermal injection method,or by anion exchange method at room temperature,and both of them have almost the same luminous properties;therefore,a variety of synthetic methods and excellent photoelectric performance makes the perovskite quantum dots has a broader prospect in the field of lighting LED.However,phosphor-converted LEDs based on perovskite quantum dot are less stable at high temperatures or in air conditions,limiting the performance of perovskite quantum dots on devices.In order to overcome this problem,we have made adjustments and optimization of the external structure of the color-conversion layer of the perovskite quantum dot-based LED device.The main research content of this paper through the design of light-emitting layer and its application is as follows:On one thing,the liquid quantum dots as color-conversion layer instead of solid-state phosphor quantum dots to prepare a variety of monochrome LED devices.Firstly,the perovskite quantum dots with different emission wavelengths were prepared and their basic characteristics such as absorption spectrum,luminescence spectrum and transmission electron microscope were measured.The absorption and photoluminescence spectra show that the quantum dots absorb and emit light coverage over the entire visible light emission regions.The transmission electron microscopy shows that the quantum dot particles' sizes are uniform and have a good monodisperse.At the same driving current,we measured the luminous intensity of the quantum dot excited by the blue LED chip,and found that the luminous intensity first increased and then decreased.At this time,the concentration of quantum dots corresponding to the maximum luminous intensity was found,and monochromatic LED devices were prepared at this concentration,and then their luminous efficiency,external quantum efficiency and device stability were measured.On the other hand,the red emission perovskite quantum dot solution as color-conversion layer was applied to the preparation of the warm white LED.Firstly,three kinds of quantum dots with different emission wavelengths were prepared,which were combined with white LED based on YAG phosphor.And then the luminous efficiency and color rendering index of the YAG phosphor-based white LED and the as-prepared white LED were tested under the same driving temperature and the same color temperature.The optimal quantum dots were found and the LED devices with different color temperature were prepared based on this quantum dots.Finally,preparing the phosphor-based LED by using the above quantum dots,and under the same conditions,two kinds of devices were prepared for comparison to measure their stability: one is liquid quantum dots device,and the other is solid-state phosphor-based LED device;and then found that liquid quantum dot-based LED device are more stable.Finally,for the liquid quantum dot-based LED,the color temperature,color coordinates,color rendering index and other indicators to make further stability test.