Perovskite Quantum Dot Random Lasing Enhanced By Employing PMMA And Metal Nanoparticles

Compared with conventional lasers,random lasers do not have an optical resonator,and the optical feedback is mainly provided by multiple scattering in random media.In a disordered nano-medium system,multiple scattering will occur when the scattering intensity is sufficient.When the scattered photons return to the initial scattering position,a closed loop can be formed to realize the local resonance of light.Random lasers have many advantages such as simple manufacturing process,low cost,easy integration,etc.,which have attracted wide attention from researchers.All-inorganic perovskite Cs Pb X₃（X=Cl,I,Br）quantum dots（QDs）,as a gain material with excellent photophysical properties,has received extensive attention in recent years.Due to the unique localized surface plasmon resonance（LSPR）of metal nanoparticles（NPs）,the electric field can be confined around the surface of the metal nanoparticles.The generated strong electric field can effectively increase the photonic mode density around metal nanoparticles,and is widely used to enhance the lasing performance.According to the LSPR of metal NPs,a simple method using PMMA and Ag nanoislands to improve the performance of Cs Pb Br₃ film random laser is proposed,which is based on a"sandwich"structure of PMMA/Ag-Cs Pb Br₃-glass substrates.Through the surface passivation effect and symmetrical waveguide effect of PMMA and LSPR induced by Ag nanoislands,a low threshold（～2.6 m J/cm²）coherence random lasing was successfully obtained in the"sandwich"system.By comparing the photoluminescence（PL）spectrum and the PL lifetime of the Cs Pb Br₃ film before and after the addition of PMMA,it is found that the PMMA can increase the PL intensity of the Cs Pb Br₃ film and increase the lifetime of QDs.The PMMA coating improves the stability of the perovskite film continuously pumped by the laser in the air,so that Cs Pb Br₃ QDs film can maintain good performance even under continuous pumping for 2 hours,which helps to solve the instability problem of Cs Pb Br₃ QDs lasers.Our experiment may provide inspiration for all inorganic lead halide perovskite light-emitting devices,especially continuous wave pumped lasers and electrically driven perovskite lasers in the future.In the SiO₂-QDs-SiO₂（SQS）composite nanostructure doped Ag nanoislands system,a stable random laser is realized.The QDs we investigated are Cs Pb Br₃.In this system,SiO₂microspheres with large volume can provide high scattering.The high scattering effect formed by SiO₂ microspheres cooperate with the LSPR of metal nanoparticles provide optical feedback for the formation of random lasers.Therefore,the coherent random laser with a low threshold～2.2 m J/cm² is successfully obtained.The Cs Pb Br₃ QDs anchored by SiO₂microspheres avoid the Photoinduced regrowth and fluorescence quenching caused by the clusters of QDs.At the same time,the amino group in 3-aminopropyltriethoxysilane（APTES）can effectively passivate the surface of the QDs to maintain a high PL quantum yield.Due to the existence of the ultra-stable SQS composite nanostructure,the SiO₂ shell effectively protects the internal QDs from water erosion,thus making Cs Pb Br₃ has a higher ability to withstand water erosion.The luminous intensity can still maintain 70%of the original intensity after adding pure water for 40 days.This kind of stable random laser based on perovskite QDs film has broad application prospects in integrated optoelectronics,display imaging and sensor measurement.