Study On Fabrication And Performance Of Ultraviolet Detection-Electroluminescence Integrated Optoelectronic Devices

Among various kinds of multifunctional integrated devices?MIDs?,ultraviolet photodetective and electroluminescent integrated devices?UP-EL IDs?is one of the most attractive devices,because it is widely applied in fabricating military and civilization equipment,such as missile warning,space transmission,high voltage corona monitoring,field fire remote sensing,biochemical testing,medical disinfection,special display,lighting and backlight.However,as an emerging frontier interdisciplinary field,research work about UP-EL IDs is still sporadic comparing with other traditional devices.Therefore,devices structures,energy transfer theory,new fabrication process and new novel material synthesis were fully investigated in my work.At the same time,their effect on UP-EL IDs and other electronics was also studied.The contents of this Ph.D.Thesis are shown as below:1.To study how exciton adjusting layer?EAL?and electron transport layer?ETL?affect electroluminescent and ultraviolet detective properties of UP-EL IDs,respectivelyFour representative organic materials as EAL to fabricate UP-EL IDs were chosen,and their performance differences were analyzed.The HOMO of EAL can remove leakage current to improve detective performance effectively when UP-EL IDs work as photodetectors;while the LUMO of EAL can increase the injection of holes to improve electroluminescent performance when UP-EL IDs work as LEDs.What's more,FDTD solution was used to confirm the thickness of EAL can be used to modify the optical distribution in devices.At the same time,the effect of five kinds of ETLs on UV detective and EL properties of UP-EL IDs was also systematically studied.The results showed that two orders of magnitude improvement of UV detectivity and 3.3-fold of luminescent intensity enhancement were achieved.The result indicated that not only the difference of LUMO between the active layer and ETL but also the variety of electron mobility showed a significant effect on UV detective and EL property of UP-EL IDs through adjusting electron injection/transport.Meanwhile,the optimized ETL thickness was beneficial for confining the leaking of holes from the active layer to cathode,leading to the decrease of dark current density for high UV detectivity.we offered a practical method on broadening EAL and ETL material selection and device architecture optimization for the fabrication of high performance UP-EL IDs.2.To realize enhancement of both electroluminescent and ultraviolet detective properties in UP-EL IDs by two triplet-triplet annihilation?TTA?materials doping system and aggregation-induced emission?AIE?doped by thermally activated delayed fluorescent?TADF?material,respectivelyOn one hand,the performance enhancement of UP-EL IDs was realized by using a TTA featured material as a host and another TTA featured material as a dopant in a doping system to be an active layer.The result showed that the UP-EL IDs with a doping system had a 7-fold enhanced maximum luminance with a lower turn-on voltage of 2.5 V.Meanwhile,the doped UP-EL IDs exhibited a high detectivity of 4.5?10¹²Jones at a bias of-1 V under the UV-350 nm illumination,which was 34.6 folds higher than that of the control device.Based on the analysis of the energy transfer model of devices,it was found that the improved electroluminescent performance of UP-EL IDs was attributed to the TTA process and efficient energy transfer from CzPhONI to NA-TNA.And by analyzing the dark current behavior of device,the high ultraviolet detective property of UP-EL IDs was caused by the merit of the energy band“carrier capture region”when the dopant NA-TNA was added into the active layer,and the energy band“carrier capture region”contributed to reducing the dark current of UP-EL IDs.On the other hand,UP-EL IDs is fabricated with an AIE featured material as the host and a TADF featured material as dopant?doping concentration including:5 wt%,10 wt%,15 wt%,20 wt%,25 wt%?in a doping system as an active layer.The 15%4CzIPN doped UP-EL IDs achieved 6,3.26,3.17 times and one order of magnitude improvement in luminescence,current efficiency,power efficiency and detectivity,respectively.The property improvement was analyzed using the theory of emission quenching suppression in the AIE process,mechanism of energy transfer from host to dopant,and simulation of section energy distribution variations in the active layer as the increase of doping concentration.Therefore,combining AIE materials with TADF materials as an active layer was also an effective way to enhance properties of UP-EL IDs.3.To utilize multistep vapour assisted deposition?MVAD?method to optimize crystallization and nanostructured surface of the perovskite film firstly and studied its effect on the UP-EL IDs performanceWe optimize the crystallization and nanostructured surface of MAPbBr₃ film through applying MVAD method.Then,we enhanced the optical field distribution and charge transfer feature of MAPbBr₃ film by establishing an optical simulation model.Based on our modifed MAPbBr₃ active layer,finally,we demonstrated a high performance UP-EL IDs with EL and ultraviolet photodetective bifunctions,which exhibits a 6.27-fold improvement of brightness and 3 orders of magnitude increase of detectivity.At the same time,the hole transport layer was no longer needed in the device to balance charge transfer,thus device structure was successfully simplified.4.To design and synthesize a novle kind of all inorganic perovskite quantum dots and evaluate its possibility for UP-EL IDs fabricationPerovskite quantum dots?PQDs?showed large potential for the field of light emission and information display for high quantum yield,narrow emission band and tunable emissive spectra.However,its commercialization way was still hindered by some obstacles epecially low thermal resistance.In this part of work,green PQDs with high thermal resistance as well as high quantum yield and narrow emission band was successfully fabricated by introducing Gallium pellet during synthesis process.This modified PQDs holded 80%of its room temperature?RT?photoluminescence?PL?intensity at 80^oC,while the pristine one maintained?16%of its RT PL intensity.Comparing with pristine sample,a quantum yield enhancement from 54%to nearly unit and an emission band decrease from 20 nm to 17 nm were also achieved in modified PQDs.Using this method,red and blue high thermal resistant PQDs,having 80%and90%of their RT PL intensity,respectively,at 80^oC were fabricated.These modified PQDs show great advantage in optical,electrical and thermal resistant properties,simultaneously.In summary,a systematic study on organic functional layers,host-guest energy transfer and MVAD were carried out,and high performance UP-EL IDs were fabricated.It can provide a good reference for the study on device structure and fundamental theory of UP-EL IDs in the future.Moreover,all inorganic PQDs with excellent thermal resistance and quantum yield were synthesized,and its possibility of usage in the UP-EL IDs fabrication was evaluated.