| Semiconductor nanocrystals（NCs）show great potential in lighting and display field due to their high quantum yield,high color purity and tunable luminescence wavelength.At present,the research of cadmium-based NCs has been relatively developed,but its toxicity seriously limits its further development,therefore it is very necessary and important to develop cadmium-free semiconductor nanocrystals.Among cadmium-free NCs,multinary copper-based chalcogenide NCs are one of the most promising materials to replace cadmium-based materials because of their abundant raw materials,simple preparation and environment-friendly.Great progress has been made in red and yellow light electroluminescent devices based on copper-based chalcogenide,but the progress of blue light electroluminescent devices is slow.As a member of the multinary copper-based chalcogenide semiconductor materials,CuGaS2 has a band gap of 2.49 e V,it can theoretically achieve blue light emission through the introduction of Zn ions,but its device efficiency needs to be further improved,and systematic research on material synthesis and device process is needed.In this paper,alloy type Cu-Ga-Zn-S（CGZS）semiconductor NCs were obtained based on the synthesis of CuGaS2 NCs through multiple injection of Zn precursor.The luminescent performance of the material is optimized by changing the precursor amount and reaction time,and electroluminescent devices were constructed through all-solution-processed.Device performance was improved by further optimizing hole transport layer（HTL）and emission layer（EML）.The main research works are as follows:1.Cubic phase CGZS NCs with luminous peak tunable in green to blue regions and excellent luminescent performance were prepared through multiple injection method.Continuous injection of Zn precursors can passivate the surface and internal defects of NCs,thus improving the photoluminescence quantum yield（PLQY）and stability of NCs.Then the luminescent performance of materials was regulated by adjusting the amounts of anions and cations and the length of carbon chain of surface ligands.The relative PLQY of CGZS NCs with luminous peak at 470 nm was over 90%,and the patterned polymer film based on these NCs had excellent blue light emission and good stability,showing its good solid-state luminescent performance.On this basis,luminescence mechanism was discussed in detail,and the transient photoluminescence results showed that the emission of CGZS NCs was dominated by DAP recombination.2.Electroluminescent（EL）devices based on CGZS NCs were successfully constructed by all-solution-processed,with the EL emission peak at 476–491 nm,and the maxium EQE of the resulting device reached 1.0%.The effects of different HTL on electroluminescent devices are studied,and the results show that using PVK as HTL can obtain blue light emission,and can effectively improve the device performance.On this basis,by optimizing the luminescent performance of CGZS NCs,the performance of blue light CGZS NCs electroluminescent devices was further improved,and its peak EQE could reach 1.0%.Moreover,EML material by using NCs prepared with n-octanethiol of shorter carbon chain as surface ligand,the EL emission peak of the device was regulated to 468 nm.Compared with the reported blue-emitting devices based on CGZS NCs,our electroluminescent devices showed decreased efficiency roll-off phenomenon with a shorter EL emission wavelength. |
