CsPbBr_3钙钛矿纳米片的制备及其发光性能

Preparation and photoelectric properties of CsPbBr_3 perovskite nanoplates

通过精确地控制在高温注入法中的制备温度和合成时间,利用高温注入法制备出了全无机CsPbBr_3钙钛矿纳米片(nanoplates,NPs),并将所制备出来的CsPbBr3钙钛矿纳米片用简单的溶液旋涂法和真空蒸镀的方法制备了以CsPbBr_3钙钛矿纳米片为钙钛矿发光层的发光二极管(light emitting diodes, LEDs).同时对CsPbBr3钙钛矿纳米片的结构、形貌和光学性能及以CsPbBr3钙钛矿纳米片为钙钛矿发光层的LEDs的光电性能进行了表征和分析.分析表明,利用经本文改良过的高温注入法可以获得尺寸均一的CsPbBr3钙钛矿纳米片,并且具有良好的光学性能.通过使用溶液法所制备出的以CsPbBr_3钙钛矿纳米片为发光层的LEDs器件的外部量子效率(externalquantum efficiency, EQE)为1.71%.

All inorganic cesium lead halide(CsPbX3,X=Cl,Br,I)perovskites,as a best candidate in perovskite family,have attracted great interest due to their fascinating optical,chemical and semiconducting properties and have demonstrated as potential building blocks in various applications such as photodetectors,light-emitting diodes,solar cells and lasers.Numerous efforts have been made to develop various CsPbBr3 perovskites with tunable morphology such as quantum dots(0-D),nanowires(1-D)and nanoplates(2-D)to achieve desired properties.Among them,anisotropic colloidal quasitwo-dimensional nanoplates have been attracting a great deal of research enthusiasm.In this work,all-inorganic CsPbBr3 perovskite nanoplates were prepared by precisely controlling the synthesis temperature and time in the hot-injection method.The reaction was performed under the protective atmosphere of nitrogen,at 110°C for 5 s and the reaction mixture was cooled by ice-water bath.Afterwards,the solution was purified by centrifugation at 12000 r min-1 and the precipitates were dissolved in n-octane.The structure,morphology and optical properties of as-synthesized CsPbBr3 perovskite nanoplates were characterized and analyzed by the series of characterization techniques.The results show that a sharp PL emission was detected at the peak of 500 nm with a narrow full width at the half maximum(FWHM)of 26 nm.The high-resolution transmission electron microscopy(HR-TEM)showed that the as-prepared CsPbBr3 nanoplates were uniform in size,with an average length of 20–21 nm and a thickness of 3–5 nm.All the above studies evidenced that,the improved high temperature-injection method have yielded the CsPbBr3 perovskite nanoplates with uniform size distribution,high color purity and improved optical properties.In addition,light emitting diode(LED)with CsPbBr3 perovskite nanoplates as the perovskite luminescent layer were fabricated by the simple solution spin-coating and vacuum evaporation technique.The device structure of the LED is ITO/PEDOT:PSS/TFB/CsPbBr3 NPs/TPBI/LiF/Al.In the device configuration,the patterned ITO is used as the anode,the spin-coated TFB with larger hole mobility is used as the hole transport layer,vacuum evaporated TPBI is chosen as the electron transport layer,as-prepared CsPbBr3 perovskite nanoplates are used as the light emitting active layer,and the vacuum evaporated LiF as the electron injection layer with Al cathode.The external quantum efficiency(EQE)of 1.71%and the luminous brightness of 297 cd m-2 was achieved for the LED devices fabricated by the solution method.Moreover,the densification and roughness of CsPbBr3 perovskite nanoplates as the luminescent layers were measured by atomic force microscopy(AFM).The improved efficiency and performance of our device was directly related to the compact and smooth surface of CsPbBr3 luminescent active layer.This result lays a foundation for the fabrication of high efficiency light emitting diode devices by utilizing all-inorganic CsPbBr3,and provides a relatively simple method for the synthesis of CsPbBr3 nanoplates,as well as good repeatability of thin film device fabrication process.