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PHOTOVOLTAIC AND THERMAL PROPERTIES OF HYBRID ORGANIC-INORGANIC METAL HALIDE PEROVSKITES

Kovalsky, Anton
http://rave.ohiolink.edu/etdc/view?acc_num=case1500584556606705

Abstract Details

2017, Doctor of Philosophy, Case Western Reserve University, Chemistry.
This dissertation focuses on intrinsic and emergent properties of a novel crystalline compound, methylammonium lead iodide perovskite, a material that has been at the center of intense research for the last decade due both to its unusual hybrid organic-inorganic crystal structure and its promising photovoltaic performance. The research contained herein approaches this material from two distinct perspectives. The first half of this thesis aims to provide a rigorous characterization of the perovskite’s behavior as a light absorber and photoconverter within the context of a thin film solar cell. By systematically tracking the wavelength-dependent light harvesting and photocoversion efficiencies of perovskite-based solar, and by comparing these efficiencies across perovskite-based solar cells with certain architectural modifications, we acquire a more complete understanding of the origin of photovoltaic action of the perovskite, and are thus able to determine some clear design rules that maximize the emergent properties for which this material has become so well known. Importantly, in this first half of the dissertation, we provide detailed instructions on how to perform such rigorous analysis of solar cell technology in general. This analytical paradigm, known as combined optical and electronic loss analysis, can be used to build a thorough understanding of the specific strengths and weaknesses of either individual solar cells or entire classes of solar cells. Our analysis of perovskite-based solar cells that employ TiO2 as the electron-transporting layer provides insight both into the limitations of popular photovoltaic motifs – namely that of the ubiquitous mesoporous solar cell – for this important class of absorber, as well as the limitations of the analysis itself, and we discuss in detail the importance of correctly accounting for the effects of diffuse light scattering. The second half of this dissertation explores the intrinsic thermal properties of methylammonium lead iodide. Bulk thermal conductivity measurements performed on pellets of compressed methylammonium lead iodide, as well as some reference materials, yield a wealth of information on the vibrational properties of the perovskite’s unique unit cell. Our work represents a much needed definitive empirical demonstration of the effect of molecular motion of the methylammonium cation on thermal transport in the perovskite lattice. Furthermore, the organic-inorganic compound’s intrinsic thermal instability is also explored using thermal analysis. The thermal instability of methylammonium lead halides is a widely discussed problem in the field of perovskite-based solar cells, and is perhaps the greatest hurdle that this technology must overcome for costeffective commercialization. One of the key factors that exacerbates this issue is the extremely low thermal conductivity of methylammonium lead iodide. We use thermal analysis and crystallographic characterization to show that it is potentially possible to mitigate this issue. In the last chapter of this dissertation, we present a proof-of concept study that suggests that a controlled partial degradation can significantly raise a bulk perovskite’s thermal conductivity, even while most of the perovskite lattice remains intact. Taken together, our analyses of methylammonium lead iodide either as a light absorber or as a heat (non-)conductor point towards a plethora of possible nanoengineering strategies that can improve the stability and photocurrent generation in this important new class of photovoltaic material.
Clemens Burda (Advisor)
160 p.
Chemistry

Recommended Citations

Citations

  • Kovalsky, A. (2017). PHOTOVOLTAIC AND THERMAL PROPERTIES OF HYBRID ORGANIC-INORGANIC METAL HALIDE PEROVSKITES [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1500584556606705

    APA Style (7th edition)

  • Kovalsky, Anton. PHOTOVOLTAIC AND THERMAL PROPERTIES OF HYBRID ORGANIC-INORGANIC METAL HALIDE PEROVSKITES. 2017. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1500584556606705.

    MLA Style (8th edition)

  • Kovalsky, Anton. "PHOTOVOLTAIC AND THERMAL PROPERTIES OF HYBRID ORGANIC-INORGANIC METAL HALIDE PEROVSKITES." Doctoral dissertation, Case Western Reserve University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1500584556606705

    Chicago Manual of Style (17th edition)

case1500584556606705
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© 2017, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.