| Metal halide perovskite is one of promising emitting candidate materials for light-emitting diode(LED)due to its excellent optoelectronic properties and low-cost fabrication process.Most efficient perovskite LEDs utilize low dimensional perovskites,which exhibiting high exciton binding energy and less defect states,as emitting layers and the device efficiency and luminance are comparable to that of organic LEDs(OLEDs).However,the exploration of real display applications of perovskite LED still lacks attention.Additionally,perovskite LEDs generally displays poor operational stability.Even under low luminance of 100 cd/m2,the half-lifetime of efficient devices are only approximately 100 hours,which lags far behind the commercial OLEDs.Many factors could affect the stability of perovskite,such as Joule heat generated during device operation,ion migration induced by electric field and water/oxygen penetration in ambient atmosphere.These factors would eventually lead to degradation of perovskite layer and deterioration of LED devices.Herein,we substitute indium tin oxide(ITO)glass substrate/electrode with monocrystal silicon(c-Si)substrate/electrode in order to solve the aforementioned problems.Quasi two-dimensional perovskite with excellent water/oxygen resistance and high photoluminescence is used as light-emitting layer.The device structure could effectively avoid indium and tin diffusion as well as Joule heating.The device stability under high current injection is dramatically improved and efficiency droop is suppressed.Through inserting a passivation layer at silicon rear side and tuning charge transfer balance,c-Si-based perovskite LED achieves the record efficiency and luminance.Furthermore,this paper makes a preliminary exploration of perovskite LED display applications,and realizes the dynamic and static display of c-Si-based devices.Main work is shown as follows:1.A perovskite LED architecture is built via combining p-type c-Si(p-Si)with quasitwo-dimensional CsPbBr3 perovskite.P-Si,poly(N-vinylcarbazole)(PVK)and 2,2',2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)(TPBi)are used for hole injection,hole transport and electron transport,respectively.Through designing transparency and electrical conductivity of top semitransparent electrode,light could be extracted from Ag/p-Si/PVK/Perovskite/TPBi/LiF/Al/Ag device structure.An external quantum efficiency(EQE)of 0.026%and a luminance of 1000 cd/m2 are obtained.Furthermore,ultra-thin natural silicon oxide layers were used to tune charge transport balance.Finally,the turn-on voltage decreases from 4.1 V to 3.5 V and EQE increases to 0.15%.2.By introducing poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-butylphenyl)(TFB)as buffer layer,charge balance is further improved and surface defects of silicon are reduced.The resulting EQE and luminance of TFB-inserted device reach 2,12%and 2500 cd/m2.Device surface temperature is detected.Benefiting from excellent heat dissipation of silicon,device displays uniform temperature distribution at different current densities.At a current density of 300mA/cm2,c-Si-based device surface temperature only increases 5?.Compared with ITO/glass-based devices(reference devices),the lower operating temperature facilitates extended operational half-lifetime of 17 minutes at the high current density,which is a 113-times enhancement than reference devices.Moreover,efficiency droop phenomenon in reference devices is also significantly suppressed.3.In order to realize the perovskite LED display applications,we build hardware platform and develop program for dynamic display.Well-designed top electrodes of seven independent silicon-based devices are combined to show a digital pattern.Different patterns are realized by precisely controlling the ON/OFF state of the seven cathodes through program.Due to rational device structure design,the display process exhibits low latency and high brightness.Static pattern display is implemented.Patterned top electrode is designed to realize electroluminescent logo display.For complicated pattern,inkjet-printing technology is applied for perovskite deposition.Logo of Soochow University and panda pattern are realized,from small size(1 cm×1.5 cm)to large size(4.5 cm×5 cm).The electroluminescent perovskite ink dots are arranged neatly with 125 ?m of dot spacing and a resulting resolution of 200 dpi(dots per inch)is obtained. |
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