Study of Methylammonium Lead Triiodide Intrinsic Stability and Solid-Solution behaviour in Mixed Halide Perovskite Systems

• Author / Creator

  Askar, Abdelrahman Mostafa Mohamed Sanad

• Over the last nine years, a new class of materials named lead halide perovskite has made a paradigm shift in the field of optoelectronic solution-processable low-cost and
  high-efficiency devices, with outstanding accomplishments especially in the ever-growing field of renewable solar energy harvesting. With current state-of-the-art 22.7%
  efficiency for lab-scale perovskite solar cells, the expectations are high with the potentials of this "magic" material system in being a real driving force for next-generation low-cost and high-efficiency photovoltaics technology.

  In order to make maximum use of any newly introduced material systems such as halide perovskites for real-life applications, it is essential to carry out fundamental
  studies which enable better in-depth understanding of the basic material electrical, optical, thermal, mechanical, etc. properties. This understanding is crucial for such a
  new technology to be able to advance further into actual products in the market.

  In this work, we tried to shed light on fundamental questions pertaining to important lead halide perovskite material characteristics. We studied the stability of methylamonium
  lead iodide (MAPbI3) through identifying all possible decomposition products of MAPbI3, which each has a unique fingerprint. Through systematic investigation of potential decomposition pathways under diffierent conditions of humidity and/or heat, we identified a comprehensive understanding of the intrinsic stability of MAPbI3. We
  hypothesized that the lower stability observed in films is mainly due to the preparation protocols and that the MAPbI3 is more resilient than what was previously thought.

  Also, we studied two of the main lead halide perovskite materials which are routinely used nowadays in the realization of high-efficiency and relatively-stable perovskite solar
  cells, namely methylamonium and formamidinium lead mixed halide perovskites. We explored the potential of a new synthetic route (mechanochemical synthesis) to prepare
  these materials with deffinitive control over stoichiometry. It has been reported earlier in the literature that these systems suffer from halide phase segregation, so we investigated
  this through adopting a suite of advanced characterization with atomic-scale probing capabilities which confirmed that these systems behave like a solid-solution with atomic scale halide mixing.

  The significance of the results presented here is vital for future research in this rapidly growing field as these results answer fundamental questions related to the perovskite materials intrinsic properties as well as elaborating on new up-scalable synthesis techniques.

• Subjects / Keywords

  • NMR
  • Solid-solution
  • solid-state NMR
  • Perovskite
  • Mixed halide perovskite
  • Stability

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3FT8F13G

• License

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