Study On Optoelectronic Performances Of Low-lead Halide Perovskite LEDs

Organic and inorganic metal halide perovskite has become the best choice for the next generation of LED due to its remarkable optoelectronic properties,ultra-high carrier mobility and easy preparation process.At present,the external quantum efficiency of red and green light has exceeded 20%,reaching the commercial level,while the external quantum efficiency of blue perovskite LED is still very low.Nowadays,the research on perovskite LED focuses on its internal mechanism,the improvement of blue perovskite LED efficiency and low lead.The study of low lead is often use Sn²⁺or Mn²⁺to replace or partially replace Pb²⁺in the B site of perovskite,because the Pb is harm for environment.Nowadays,neither Sn²⁺nor Mn²⁺can not greatly improve the efficiency of perovskite LED.In this paper,we innovatively use Ge²⁺to partially replace Pb²⁺to achieve a breakthrough in the external quantum efficiency of low lead perovskite LEDs from less than 4%to 13.1%.In this paper,40%phenylethyl ammonium bromide(PEABr)was mix into Cs Pb_1-XGe_xBr₃(x=0?0.5)three-dimensional perovskite Cs Pb_1-XGe_xBr₃(x=0?0.5)to form a multi-quantum well structure,and then passivating agent was used to effectively reduce the intrinsic defect density.Through SEM,AFM and XRD morphology and characterization analysis,we found that the morphology and structure of Ge changed greatly when the Ge content was about 30%.Therefore,it was speculated that the maximum proportion of Ge involved in coordination might be around 30%.Optical measurements of thin films show the same pattern.Through PLQY experiment,we found that Germanium would have a positive impact on the photoluminescence efficiency of the film,and the film efficiency was significantly increased from 40%to71%after a small amount of Ge replaced Pb.When Ge content reaches 30%,PLQY efficiency drops rapidly.By measuring the fluorescence life of Ge doped perovskite,it can be found that the radiation combination dominates the film before the Ge content is 20%,so PLQY increase,while the radiation combination dominates the film after the Ge content exceeds 20%,and PLQY decreases.The ITO/PEDOT:PSS/PVK/perovskite/TPBi/Li F/Al device structure was used to fabricate Pe LEDs,the transport layer on the device to adjust and control the concentration and thickness of the final to make the external quantum efficiency value of 13.1%,the largest brightness is 10313 cd/m².Later,the SCLC method was used to carry out single-load tests on Ge-doped devices,and it was found that with the increase of Ge content,the density of defect states also increased,It's not consistent with the TCSPC.Therefore,PVK substrate may not be the most suitable substrate for Ge-doped perovskite,Ge-doped perovskite LED still has great potential.