| Luminescent materials hold wide applications in military and civilian fields,such as lighting,display,communication,sensing,imaging and photodetecting devices.With the increasing requirement of comfortable and high quality lighting and display equipment,the commercial white light-emitting diodes（WLEDs）based on rare metal ions are far from the high color rendering index devices due to the lack of red light component.Besides,these luminescent materials usually emit wide light,exhibiting low color saturation.Though organic LEDs（OLEDs）are claimed to be potential candidates,they suffer from high cost,low yield and difficulties in large area displays.As a result,OLED displays are only widely applied in phone while the televisions are expensive.The flexible tunability of emission color of luminescent nanocrystals（NCs）endows them with potential applications in the next generation displays.The high quality red emission and narrow line width can compensate for the rare metal phosphors well.However,most of the related patents are in two companies,and the highly toxic cadmium and rare indium have been the obstacles of wide applications.Besides,short emission colors are usually obtained via decreasing size,which results in low reproducibility and low stability.Therefore,NCs with relatively lower toxicity,low cost,and high quality are in urgent need.This thesis is focusing on the synthesis of a new kind of all inorganic halide perovskite（IHP）NCs.Several low-cost,mass-production approaches are developed for the fabrication of IHP NCs related matters.Some researches have been carried out in detailed about the surface chemical states,stimulated emission and related applications.The work summarized as follows.1)We developed a hot-injection method for the preparation of IHP NCs.The emission color can be easily tuned from 405 to 650 nm via controlling the anion compositions.The NCs possess high photoluminescence quantum yield up to 90%and wide color gamut covering up to140%of the NTSC color standard.Syngestic effect of high exciton binding energy（40 meV）,surface self-passivation by halide atoms,and quantum well like structure was proposed and proved to contribute to the high quantum yield.Based on such excellent NCs,stimulated emission(22μJ cm-2)and lasing(11 mJ cm-2)with low thresholds are achieved.Additionally,low threshold is assigned to the high biexciton binding energy（50 meV）and faster recombination rate（smaller than 50 ps,which is faster than Auger recombination,105 ps）.2)We developed a room temperature supersaturation recrystallization strategy for the synthesis of NCs.No heat and inert atmosphere are needed that the cost is restively lower,which make it possible for large scale production.LEDs with color temperature from 2500 to 11500 K are obtained,as well as the pure white color.Two-photon absorption and photoluminescence are observed,which are applied for optical limiting application.Finally,the NCs/PMMA film exhibits a limiting threshold of 2.8 J cm-23)We developed a one-pot synthetic method for the fabrication of IHP luminescent phosphors.All the precursors,including aminated silica spheres,solvent,surfactants,and chemicals,are put into a vessel directly.After being heated in the air for several minutes,highly luminescent composites are obtained.Owing to the separation effect of silica spheres,the environmental and optical stabilities are improved greatly.In addition,according to the strong scattering effect of silica spheres and efficient optical gain effect of IHP NCs,random lasing without cavity is achieved with a threshold of 40μJ cm-2.This will open a window of IHP based multifunctional materials.4)We developed a room temperature healing method of IHP films.During the purifying of NCs and stirring of large particles in solvents with surfactants,the size of IHP can be tuned between several nanometers and microns reversibly.According to this phenomenon,IHP films with pinholes and cracks resulting from the evaporation of solvent become compact and smooth after treating.The responsivity,external quantum efficiency,and the response speed are improved greatly.Considering the low responsivity of IHP photodetectors,fast carrier tracks are constructed within the IHP films.The highest responsivity(31.1 A W-1)and external quantum efficiency（7488%）among IHP photodetectors are obtained.5)We proposed a new encryption technique for photocommunication.By controlling the thickness of IHP films,photodetectors with visible and infrared dual mode detective abilities are fabricated.The full width at half maximum is as narrow as 13.6 nm,which is the smallest value up to date for narrow band photodetectors.Based on the highly spectrally selective detections,encryption technique with pure photodetectors are proposed,which holds great potentials in future security communication and also provides new opportunities and platforms for encryption techniques. |
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