• Login
    View Item 
    •   Home
    • Theses & Dissertations
    • 2016 - Mines Theses & Dissertations
    • View Item
    •   Home
    • Theses & Dissertations
    • 2016 - Mines Theses & Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of Mines RepositoryCommunitiesPublication DateAuthorsTitlesSubjectsThis CollectionPublication DateAuthorsTitlesSubjects

    My Account

    Login

    Mines Links

    Arthur Lakes LibraryColorado School of Mines

    Statistics

    Display Statistics

    Understanding efficiency improvement in organic photovoltaics with molecular modifiers

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Braid_mines_0052E_11003.pdf
    Size:
    2.542Mb
    Format:
    PDF
    Download
    Author
    Braid, Jennifer L.
    Advisor
    Collins, Reuben T.
    Kopidakis, Nikos
    Date issued
    2016
    Keywords
    cross-sectional potential mapping
    Kelvin probe microscopy
    molecular modification
    organic photovoltaics
    transparent conducting oxide
    work function tuning
    
    Metadata
    Show full item record
    URI
    https://hdl.handle.net/11124/170113
    Abstract
    Molecular dipole modification of metal oxides has become popular to improve the performance of organic photovoltaic devices through charge transport level matching to the bulk heterojunction species. Properly tuning the work function of a device interlayer can increase charge collection from the active layer, ultimately raising the efficiency of the device. Here a novel type of molecule is introduced for modulating the work function of charge transport layers in organic photovoltaics: the conjugated phosphonic acid. Due to its longer and double-bonded linkage, as well as its multi-dentate attachment, this type of molecule is shown to shift the work functions of ZnO and ITO through ranges of 2 eV. The vast dipolar aromatic groups possible in conjugated phosphonic acids allow for either increasing or decreasing the work function of the substrate incrementally. This facilitates the energy matching with the Fermi level of a photovoltaic material necessary to achieve maximum efficiency of that solar cell. The effectiveness of conjugated phosphonic acids is also demonstrated in an operational organic bulk heterojunction solar cell. A self-assembled monolayer of conjugated phosphonic acid on the electron transport layer of an inverted device is shown to significantly increase the power conversion efficiency of that cell, even compared to its non-conjugated counterpart. The improvement to device performance was largely due to an increase in the short circuit current, with minor boosts to the open circuit voltage and fill factor. Direct measurements of potential distributions inside phosphonic acid modified and unmodified cells are also given. Beneficial modification of the electron transport layer interface is shown to extend the electric field within the active layer. The electric field is thought to aid in carrier separation and extraction from the bulk heterojunction, which correlates with improved short circuit current. Additionally, the technique for measuring potential distributions within operational solar cells, cross-sectional scanning Kelvin probe microscopy (X-SKPM), is tested in ambient and inert conditions. X-SKPM of organic photovoltaics in air reveals oxygen p-doping of the bulk heterojunction, as well as sensitivity to surface contamination of oxide interlayers, while inert conditions facilitate a reliable measurement of the potential distribution in organic photovoltaics.
    Rights
    Copyright of the original work is retained by the author.
    Collections
    2016 - Mines Theses & Dissertations

    entitlement

     
    DSpace software (copyright © 2002 - 2023)  DuraSpace
    Quick Guide | Contact Us
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.