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Synthesis and Stability Improvement of Perovskite QDs for Optoelectronic Devices

Hasanzadeh Azar, Mahdi | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52667 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Simchi, Abdol Reza
  7. Abstract:
  8. In the last years, perovskite QDs have emerged as the novel candidate due to their unique optical properties such as high-absorption coefficient, long-range charge transport, low exciton-binding energy, and etc. Nonetheless, poor stability of perovskite in ambient conditions made researchers to consider this issue. Recently, amoung various types of organic-inorganic perovskites, Formamidinium lead iodide has attracted tremendous attention due to its near IR absorption wavelength in addition to the higher stability compared to MAPbI3. In this work, FAPbI3 perovskite stability improvement was investigated by several methods under different conditions. In the first step, FAPbI3 QDs colloidal solution was prepared utilizing Oleic acid and Octylamine as surfactants in room temperature. HRTEM results showed that the size of spherical nanoparticles was around 10.6 nanometer. According to the Photoluminescence test results, this stable colloidal solution retained 85% of its original photoluminescence intensity after 1 month. It proved that an employed Acetonitrile as the precursor’s solvent was effective to preserve alpha phase of FAPbI3 QDs with amazing optical properties against deleterious environmental factors. For enhancement of QDs stability under high temperatures and moisture, (3-Aminopropyl) triethoxysilane was employed. This ligand was able to control the growth rate of QDs and could stabilize them under aforementioned conditions. Transmission electron microscopy verified that core/shell structure of QDs/silica was formed which QDs were embedded in wide silica matrix after 4 h of hydrolysis process. Preserving 96% of its original photoluminescence intensity after 1 month in 60% moisture showed that this structure was effective to increase perovskite QDs stability in moist situations. In addition, higher thermal stability than QDs-ligand structure was observed by TGA test. In the final step, by changing of Formamidinium amount, Nano plates of FAPbI3 were formed for the first time without using long-chain amine ligands. Based on observations, FAPbI3 nanoplate’s film emission could remain more than 6 months, apparently. As it was proved, 2D structure of perovskite materials has higher stability than the other morphologies.On the other hand, FAPbI3 QDs were synthesized consuming Mercaptopropionic acid and octylamine ligands at room temperature. Finally, the solar cell device was fabricated depositing FAPbI3 QDs on the surface of MAPbI3 film. I-V curve results demonstrated that the efficiency was increased from 11.40 to 14.70 percent for without and with FAPbI3 QDs, respectively. In addition, all parameters such as Voc, Jsc and FF were increased by adding FAPbI3 QDs
  9. Keywords:
  10. Quantum Dot ; Perovskite ; Solar Cells ; Perovskite-Based Solar Cell ; Two Dimentional Perovskite Nanoplates ; Formamidinium Lead Iodide

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