Preparation And Application Of Carbon Dots Fluorescent Films In Light-emitting Devices

As an emerging fluorescent nanomaterial,carbon dots have attracted widespread attention due to their low toxicity,low cost,high stability,and good fluorescence performance,and have great potential in the field of light-emitting devices.As the luminescent layer of light-emitting devices,carbon dots generally need to be doped with the main material to form a film.On the one hand,for places with low lighting requirements,the preparation method of carbon dot films is relatively cumbersome,and the film forming process needs to be simplified to meet the needs of large-scale production as much as possible;On the other hand,for lighting places requiring high color purity display and high brightness,the color purity and quantum yield of carbon dots need to be further improved.In order to promote the development and application of carbon dots films in the field of light-emitting devices,we have designed and studied carbon dots and carbon dot thin films from the above perspectives.The main research content is as follows:（1）In order to solve the problem of cumbersome preparation methods for carbon dot thin films,a new method for in-situ preparation of carbon dot photoluminescent diode films has been proposed,which allows carbon dots to grow in situ in resin.Firstly,ammonium citrate was used as a precursor and co extruded with low-density polyethylene in a twin screw extruder to obtain a blue fluorescent film,which was applied to blue LED with a luminous efficiency of36 lm/W.In addition,white fluorescent thin films were prepared using citric acid and boric acid as precursors.The thin films were applied to photoluminescent LEDs to obtain LED devices with cold white light and positive white light.The chromaticity coordinate were（0.30,0.31）and（0.32,0.34）,and the luminous efficiency was 35 and 32 lm/W,respectively,which can meet the requirements of daily use.（2）In order to obtain carbon dots with high quantum yield and apply them to LEDs,orange emission carbon dots（O-CDs）with quantum yield up to 75%were obtained by solvothermal reaction using diethylenetriamine and Phloxine B as precursors.We have made fluorescent films of O-CDs and polydimethylsiloxane,and placed them in different stacking sequences with other fluorescent films to prepare white light photoluminescent LEDs.They have properties of cold white light,warm white light,and positive white light,respectively.The luminous efficiency ranges from 45 to 55 lm/W,which is suitable for high lighting demand and different color temperature lighting needs.The PDMS fluorescent films have certain flexibility and tensile strength,it has certain application prospects in flexible display.（3）In order to obtain carbon dots with high color purity and apply them to electroluminescent devices,we selected p-hydroxybenzaldehyde and pyrrole as precursors,and propionic acid as solvent for solvothermal reaction to obtain narrow emission deep red carbon dots（R-CDs）with a half peak width of only28 nm.Applying R-CDs to electroluminescence,we spin coated a mixed solution of PVK and R-CDs into a film to prepare an electroluminescent device.The device exhibits deep red emission and good monochromaticity（FWHM=30 nm）,with a maximum brightness of 460 cd·m^-2.In addition,we have combined R-CDs with polyvinyl pyrrolidone films for use in photoluminescent devices to obtain deep red LEDs with a peak width at half width of 30 nm,which can be used in places with high color gamut displays.