Device Research Of Perovskite Light-emitting Diodes With Deep-blue Emission

Metal halide perovskites are considered to be ideal materials for future applications in the field of lighting due to their excellent photoelectric properties(such as high carrier mobility,high photoluminescence quantum yield(PLQY),high color purity,etc.).In recent years,perovskite light-emitting diodes(LEDs)have developed rapidly,and the external quantum efficiency(EQE)of LED devices with green and red emission has exceeded 20%.However,the EQE and stability of blue(especially deep-blue)perovskite LEDs are still far behind that of red and green counterparts,which severely limits the application of perovskite LEDs in high-performance wide-color gamut display and the field of white light illumination.Therefore,the realization of blue and deep-blue perovskite LEDs with high-efficiency and high-stability is of great significance.This thesis focuses on the realization of high-performance blue and deep-blue perovskite LEDs,including materials design,device optimization and mechanism study.1.The mixed halide perovskites generally suffer from severe redshift of the electroluminescence spectral during their operation.Therefore we firstly consider single halide perovskite system with target deep-blue emission(450-460 nm).We explored the perovskite materials based on the ABCl₃ structure,which contains only chloride in“X”position.We focused on adjusting the absorption edge to the target deep-blue wavelength by tuning the components of the A site and B site ions in ABCl₃ perovskites,and fabricated the relavent LED devices.2.Color-stable deep-blue perovskite LEDs based on trichloro(3,3,3-trifluoropropyl)silane post-treatment.We drip the trichloro(3,3,3-trifluoropropyl)silane solution on the as-prepared sky-blue perovskite films to let them react with each other.In this process,trichloro(3,3,3)-Trifluoropropyl)silane can hydrolyze with the trace water in glove box and release HCl,and the HCl can realize an anion exchange reaction with the as-prepared sky-blue perovskite film.By controlling the reaction time,the ratio of chloride to bromide in the perovskite film can be tuned,obtaining the perovskite film with deep-blue emission.At the same time,some of the hydroxyl groups in the hydrolyzed silane molecule undergo a cross-linking reaction and exist on the surface of the perovskite film and the other can form hydrogen bonds with the halogen ions,which can help to relieve the phase segregation of the mixed halide perovskite.Utilizing this strategy,a deep blue perovskite LED with an electroluminescence peak at 458nm,a maximum EQE of 1.1%,and a maximum luminance of 130 cd m^-2 is achieved.The CIE coordinates is(0.146,0.045),which meets the requirements of the International Telecommunication Union's latest Rec.2020 standard that requires CIE_y value of the blue color to be below 0.046.