Research On Light-emitting And Storage Devices Based On Organic Solid Materials

With the rapid development of the electronic information technologies,the miniaturization of electronic device size is the general trend,so it is urgent to improve the comprehensive performance of electronic devices.With the increasing scarcity of inorganic materials and the size of devices based on inorganic materials approaching the theoretical limit,the development of traditional inorganic electronic devices has hit a bottleneck.In contrast,organic optoelectronic devices have many advantages,such as low-cost preparation of organic materials,easy structural modification,large area and intrinsic flexibility,which have attracted numerous attention of scientific communities.Devices based on organic solid-state optoelectronic materials find many appications including organic light-emitting diodes(OLEDs)and organic memory devices.OLEDs are widely used in solid-state lighting,flat panel display and other aspects.Among them,white light-emitting diodes(wolds)are the most widely used,but the whole device performance including device efficiency,life and emission color stability still need to be improved.Organic memory devices,including organic bistable memory(OBD)and organic field effect transistor(OFET),have also made great progress.At the same time,with the continuous improvement of the single function devices,how to endow a simple structured device with multiple functions is another key problem in the field of organic electronics.Based on this,we have carried out the following work.1.The yellow OLEDs were fabricated and optimized using the excited state proton transfer(ESIPT)organic solid-state light emitting material HBT-PA with large Stokes shift.The single molecule yellow emitting OLED achieved a relatively high external quantum efficiency(EQE)of 4.01%,pure emission color and stable CIE coordinates.This high device performance is due to the 95.12%exciton utilization of HBT-PA material in the light emitting device,via the fast reverse intersystem crossing in upper energy levels.Then,the yellow light material was hybridized with the classic thermal activated delayed fluorescence(TADF)material of DMAC-DPS to prepare the single emitting layers.By optimizing the mixing ratio,a high performance WOLED with EQE as high as13.57%,stable color coordinate and good repeatability has been demonstrated.2.A series of multifunctional organic bistable light-emitting diodes(OBLEDs)were fabricated by using solid-state light-emitting materials of DM-DCT,DCB and DCTA,respectively.The device structures are quite simple by adopting the common OLED device structures.These multifunctional devices integrate the light-emitting characteristics of OLEDs and the storage abilities of organic bistable diodes(OBDs).At low operating voltage,the device shows a write-once-read-many(WORM)nonvolatile storage behavior,with the memory switch ratio up to 10⁴and the on-/off-states stably maintained for more than 10⁴seconds.The multifunctional device is expected to be applied in the field of encrypted storage.3.The storage behavior and storage mechanism of the previously prepared small molecule OFET memory nanodevices have been thouroughly studied by various methods,including the investigations of the nannofilm surface hydrophobicities,the film roughness and surface morphology and the film surface potential difference(CPD).The storage capacity was expanded because the charge separation/recombination interface area was enlarged through the nanostructures.The storage window of 90wt%TPP-OCH₃nanodevice was up to 60 V.The stability of the device is greatly improved because the groove-like nanostructures of the charge trapping layer suppress the leakage of lateral current,while the dipole layer on the surface of the nanostructures prohibits the leakage of vertical current leakage by generating an internal electric field.The switching ratio of70wt%TPP-OCH₃nanodevice still maintains above 10⁴after 28 years of operation.