Research On Room-temperature Synthesis And Photoelectric Properties Of Red-light Perovskite Nanocrystals

As an emerging material with excellent photoelectric properties,halide perovskite minerals have shined in display,lighting,photovoltaic cells and other fields,receiving extensive attention.Among them,CsPbI₃ perovskite nanocrystals(NCs)are popular in the fields of light-emitting diodes(LEDs),solar cells and photodetectors(PDs)due to their ideal band gap,effective light absorption and high thermal stability derived from all inorganic components.However,due to the thermal unequilibrium-induced metastable(black phase)to stable(yellow phase)phase transition,the low-cost,high-yield,and easy-to-operate room-temperature synthesis method of CsPbI₃ NCs has not yet come out.In addition,the stability issues of CsPbI₃NC and the development of precise red-light perovskite materials that meet the standards of higher-definition display still need to be solved urgently.Based on the above problems,taking the iodine-based lead halide perovskite material as the main body,this thesis develops a new room-temperature synthesis method,and realizes the improvement of stability and the construction of"precise red-light"devices through doping and spectral control,which are expected to promote further application and development of perovskite materials in the display field.The main research results are summarized as follows.(1)The development of room-temperature synthesis method of CsPbI₃NCs and their application in devices.This chapter mainly studies a low-cost and high-yield room-temperature synthesis method of CsPbI₃ NCs.By introducing the dodecylbenzene sulfonic acid(DBSA)ligand,using the strong interaction between the sulfonic acid group and Pb²⁺,and the large steric hindrance of the benzene ring,the twist of the lead-iodine octahedron was successfully inhibited and the CsPbI₃ NCs was ensured stable synthesis in non-polar solvents at room temperature.XRD proved that the synthesized phase is perovskite?-CsPbI₃.In addition,based on the obtained NC,the LED has an external quantum efficiency(EQE)of 5.98%,a turn-on voltage of 2.3 V,and maximum brightness of 234 cd/m²;the PD has an on/off ratio of about200,response speeds of 22 and 93?s,and good light-stability.(2)The improvement of the stability of CsPbI₃ NCs.This chapter mainly studies a doping method to improve the stability of CsPbI₃ NCs in the air.Through B-site doping,a small-sized Zn²⁺is used to replace a part of Pb²⁺,which improves the matching of each ion size and increases the material tolerance factor.By discussing the effect of doping different content of Zn on the optical properties of NCs and the device performance,the optimal doping concentration was selected as 20%.While ensuring the excellent optical performance of NC,the stability of CsPbI₃ NCs was improved from about one day to eight days,and the EQE of the corresponding LED was increased from 5.98%to 6.98%.(3)The synthesis of"precise red-light"NCs and application of their devices.This chapter mainly studies the spectral control method of the"precise red-light"mixed halogen perovskite NC that meets the requirements of the Rec.2020 high-definition display standard.Through the control of the precursor components and anion-exchange in the post-processing process,the CsPbI₃ NCs with the emission peak at 715 nm was successfully adjusted to the"precise red-light"CsPbI_3-XBr _X NC with the emission peak at 632 nm,and the corresponding"precise red-light"LED has a turn-on voltage of 2.3 V,an EQE of 3.07%,high color purity,and good EL spectral stability.