| Summary: | 碩士 === 國立中央大學 === 物理學系 === 106 === The thesis is research of halide perovskite light-emitting diode(PeLED). Halide perovskites have recently emerged as promising for optoelectronic applications. In the field of the solar cells, its power conversion efficiency had been approached to 22%, and for the light-emitting diodes, its external quantum efficiency can higher than 11%. Halide perovskites are the new star of future display technology, they have the properties of high photoluminescence efficiency, high-colour purity, wide colour tunability and feasibility of solution-processing for low costs.
In the application of light-emitting diodes, the smaller crystalline particles in the light emitting layer have the better radiative recombination efficiency. In the first part of our experiments, we use the spin coating with the anti-solvent method to reproduce the results of the main reference. They add the surfactant of butylammonium bromide (BABr) to the perovskite (MAPbBr3) precursor solution to form a quantum dot stacked film by anti-solvent treatment via spontaneous reaction. The surface of the quantum dot is passivated by the long-chain surfactant, that is called surface passivation. They varied the ratio of BABr and MAPbBr3 to decrease the dot size.
The second part of the experiment is to apply the inverse solubility characteristics of the halide perovskite in a specific solvent. In the process of spin coating, the substrate is heated by a laser to induce nucleation of nano-crystalline in the entire film instantaneously via decreasing the solubility instantly. The more nucleus form, the smaller size of crystalline grow. Laser heating requires a high thermal stability of the material, so the material is replaced with an all-inorganic halide perovskite (CsPbBr3).
We reproduced the same trend as the results of the reference, by varied the amount of surfactant added. However, due to the design difference of the hole transport layer of the light-emitting diode, we got the uniformity film with pinholes and bad electron blocking effect, which is resulting in the external quantum efficiency of 0.5%. The second part of the results shows that the principle of using Laser heating to induce nucleation during spin coating via inverse solubility is correct. The luminance of the LED produced by this method is higher 2 times than the first part of the experiment at the same working voltage, showing its huge development potential.
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