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Fabrication and Optimization of Organic Inorganic Perovskite Solar Cells Using Vapor Phase Deposition

Sedighi, Rahime | 2017

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49682 (48)
  4. University: Sharif University of Technology
  5. Department: Institute for Nanoscience and Nanotechnology
  6. Advisor(s): Taghavinia, Nima; Tajabadi, Fariba
  7. Abstract:
  8. In this research, we focus on study and fabrication of organic inorganic solar cells. We use and optimize various methods such as one-step spin-coating, two-step sequential deposition and vapor-assisted solution process (VASP), to prepare high quality perovskite films. One-step deposition is simplest method for deposition of perovskite films. Although perovskite deposition by this method is very simple, the control of uniformity and surface film morphology is difficult. Chlorine inclusion, optimization of annealing conditions, and a sequential solution-based deposition method have been demonstrated to increase film coverage and uniformity. Hence, we use sequential deposition method for perovskite deposition. Different parameters of this method such as TiO2 thickness, concentration of the CH3NH3I solution and dipping time in the CH3NH3I solution were optimized. Finally, in optimized condition, we obtained a power conversion efficiency close to 12%. In solution based method, the high reaction rate between organic and inorganic species, presence of solvent, and dissolution of perovskite film results in incomplete coverage. VASP can be viewed as a modified two-step sequential solution deposition in which the second step is replaced by a vapor deposition process. Compared with wet solution processes, in which high reaction rate and perovskite dissolution deteriorates the film quality, VASP effectively avoids these problems by using a gas-phase reaction. In this research, we use CH3NH3Br and CH3NH3Cl for deposition of mixed halide perovskite films by VASP method, for the first time. Finally, in optimized condition we achieve maximum efficiency of 13.5, 11.6 and 10.5% for CH3NH3PbI3, CH3NH3PbI3-xClx and CH3NH3PbI3-xBrx, respectively. We replace a fraction of the CH3NH3 ions with Cs in order to optimize the optical and electrical properties of the material while maintaining the fundamental characteristics of CH3NH3PbI3. Our results show (CH3NH3)0.9Cs0.1PbI3 films have higher optical absorption and recombination resistance respect to CH3NH3PbI3 films. Hence, Cesium incorporation resulted in 20% improvement of photovoltaic performance. Furthermore, (CH3NH3)0.9Cs0.1PbI3 also exhibits better humidity stability than CH3NH3PbI3
  9. Keywords:
  10. Solar Cells ; Perovskite-Based Solar Cell ; Cesium Sorption ; Organic Inorganic Perovskites ; Vapor-assisted Solution Process ; Two-Step Sequantial Deposition

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