Synthesis Of WSe2 Quantum Dots And CaCO₃ Solutions And Their Applications In Light-emitting Diodes

Organic electroluminescent devices（OLEDs）and quantum dot electroluminescent devices（QLEDs）,as self-emitting devices,have significant advantages in terms of responsiveness,viewing angle,contrast ratio,power consumption and cost.These characteristics have led to their widespread interest and great potential for applications in areas such as new solid-state lighting and flat panel displays.UV OLEDs with short wavelength emission not only have a wide range of applications in the visible range,but also play an important role in biosensing,high-density information storage,etc.However,the carrier injection efficiency of UV OLED devices is limited by the high potential barrier between the ITO electrode and the organic functional layer.To reduce the injection barrier,novel carrier injection materials,including tungsten selenide quantum dots/carbon dots（WSe₂-QDs/CDs）,calcium carbonate（CaCO₃）,and graphene oxide（GO）,were prepared using a solution processable technique and used as an interface modification layer for ITO electrodes.By this method,the carrier injection efficiency of OLED devices was improved,and thus the modulation of the carrier balance of the devices was achieved.Meanwhile,high-performance QLED devices were prepared using WSe₂-QDs/CDs or pure CDs as light-emitting materials.The main studies are:（1）WSe₂QDs with special properties were synthesized by liquid-phase exfoliation and hydrothermal methods,and various characterization methods were performed.The results show that the WSe₂QDs have good film morphology and tunable carrier injection capability.UV OLEDs with inverted and normal structures were prepared using WSe₂QDs as the electron injection layer or hole injection layer,and the luminescence performance was tested.The maximum radiance of the inverted OLED is 1.25 m W/cm²,the maximum external quantum efficiency（EQE）is 0.48%,and the luminescence peak is located at 400 nm;the maximum radiance of the normal OLED is 1.82 m W/cm²,the maximum EQE is 1.39%,and the luminescence peak is located at 393 nm.By constructing single-carrier devices and performing impedance spectroscopy,WSe₂QDs have good electron and hole injection capability modulation properties,thus facilitating the realization of high-performance UV OLED devices.In addition,the corresponding LED devices were constructed with WSe₂-QDs/CDs as the light-emitting layer QLEDs based on WSe₂-QDs/CDs had a maximum luminance of 426 cd/m²,a luminous efficiency of 0.30 cd/A,a power efficiency of 0.13 lm/W,and an EQE of 0.40%;LEDs based on pure CDs had a maximum luminance of 214 cd/m²,a luminous efficiency is 0.31 cd/A,the power efficiency is 0.13 lm/W,and the EQE is 0.32%.（2）Aqueous CaCO₃solution and aqueous GO solution were prepared by the solution method,and UV OLED devices were constructed based on CaCO₃,GO and CaCO₃+GO composite hole injection layers.The maximum radiance of the device is 2.77 m W/cm²,the maximum EQE is 1.05%,and the electroluminescence peak is located at 396 nm.Atomic force microscopy shows that CaCO₃+GO has a good film morphology.The construction of single-carrier devices and impedance spectroscopy show that CaCO₃+GO has the ability to enhance hole injection,thus improving the performance of the devices.