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1216Wei-ChunPhDThesisFinal.pdf (21.85 MB)

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IN-SITU SOLAR CELL STUDIES OF PEROVSKITE FORMATION AND DEGRADATION

Lin, Wei-Chun
http://rave.ohiolink.edu/etdc/view?acc_num=case1491403121789203

Abstract Details

2017, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science and Engineering.
Since CH3NH3PbI3 based perovskites were discovered as viable active materials for the next generation photovoltaic devices, their instability in different environmental conditions has been a constant challenge. In pursuit of a better understanding of the degradation mechanisms, perovskite solar cells have been fabricated and investigated by scientists in order to find correlations between the solar cell characteristics/performance and the interface variation. In this thesis, the perovskite reactivity to humidity is studied by exposing samples to D2O environment for different durations. The degradation process of CH3NH3PbI3 perovskite is examined in-situ by using time-of-flight secondary ion mass spectrometry (ToF-SIMS). 3D images are constructed through the layer-by-layer spatially resolved elemental distribution analysis and the D2O moisture penetration through the sample. The intermediate products of interaction with moisture are analyzed by ToF-SIMS and X-ray photoelectron spectroscopy (XPS). We also investigated the electrical operation-induced degradation on CH3NH3PbI3 perovskite solar cells. Upon exposure to electrical current, the structure and composition were examined by combining depth-resolved imaging with ToF-SIMS, XPS and field-emission scanning electron microscopy (FE-SEM). The results show that the interface of the perovskite and the meso-porous TiO2 intermix into each other during the initial operations of solar cell. This intermixing turns the efficiency upward and improves the power conversion efficiency (PCE) up to ~50%. Both depth profiles and SEM images proved that operating devices undergo irreversible changes in thickness, which results in a dramatic performance loss eventually. In addition to studying the degradation process of the perovskite, a new formation method was developed to achieve complete conversion of PbI2 to CH3NH3I3 on FTO/Compact TiO2 substrate by employing a quaternary ammonium salt as an additive in the PbI2 solution. This complete conversion improves perovskite solar cell efficiency up to ~45 % compared to devices made without additive (from 11% to 16% in PCE).
Clemens Burda (Advisor)
David Schiraldi (Committee Chair)
Alex Jamieson (Committee Member)
Chung-Chiun Liu (Committee Member)
Xuan Gao (Committee Member)
123 p.
Chemistry; Materials Science; Molecular Chemistry; Organic Chemistry; Polymer Chemistry
Perovskite solar cells, ToF-SIMS, XPS, Depth profile, 3D image, Degradation, Degradation mechanism, Surface analysis, Elemental analysis, Humidity-induced degradation

Recommended Citations

Citations

  • Lin, W.-C. (2017). IN-SITU SOLAR CELL STUDIES OF PEROVSKITE FORMATION AND DEGRADATION [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1491403121789203

    APA Style (7th edition)

  • Lin, Wei-Chun. IN-SITU SOLAR CELL STUDIES OF PEROVSKITE FORMATION AND DEGRADATION. 2017. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1491403121789203.

    MLA Style (8th edition)

  • Lin, Wei-Chun. "IN-SITU SOLAR CELL STUDIES OF PEROVSKITE FORMATION AND DEGRADATION." Doctoral dissertation, Case Western Reserve University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1491403121789203

    Chicago Manual of Style (17th edition)

case1491403121789203
373
© 2017, some rights reserved.Creative Commons License IN-SITU SOLAR CELL STUDIES OF PEROVSKITE FORMATION AND DEGRADATION by Wei-Chun Lin is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.