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X-Ray Scattering Studies of Novel Photoactive Materials
Başlık:
X-Ray Scattering Studies of Novel Photoactive Materials
Yazar:
Harutyunyan, Boris, author.
ISBN:
9780438116023
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (162 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-11(E), Section: B.
Advisors: Michael Bedzyk Committee members: Pula Dutta; John Ketterson.
Özet:
Morphology and crystal structure of photoactive materials are key factors in determining the efficiency of solar devices. We present X-ray scattering studies of four types of photoactive systems with novel photoactive elements: perylene monoimide based nanoribbons for solar-to-fuel conversion devices, tetrathienoacene based organic dyes for dye sensitized solar cells, layered lead perovskites for solar cells and fluorinated small molecule donor for ternary bulk heterojunction solar cells.
We perform wide angle X-ray scattering measurements of perylene monoimide based nanoribbons, both in solution and deposited dry film, and develop formalism for interpreting obtained X-ray scattering patterns. This generally applicable method reproduces the measured diffraction patterns, including the asymmetric line-shapes for the Bragg reflections and yields the molecular packing arrangement within a 2D crystal structure and how it alters upon chemical modification of the constituting molecules. X-ray study of phase transition of n-propyl perylene monoimide nanostructure is discussed as well.
We used X-ray reflectivity technique to study the monolayer morphology of tetrathienoacene based dyes deposited on titanium dioxide surface. The latter serves as an electron channeling electrode in dye sensitized solar cells. Through atomic layer deposition a model surface of titanium oxide is fabricated, and organic dye monolayer deposited on it from organic solution. Analysis of X-ray reflectivity measurements expose the transformations monolayer films undergo upon alterations of backbone structure and modifications of hydrophobic alkyl chains. Alkyl chains are designed to prevent recombination and improve solubility. The results for molecular packing and molecular footprint correlate well with the measured efficiency and other characteristics of solar cells built with these dyes.
Grazing incidence wide angle X-ray scattering was further used to determine orientation of Ruddlesden-Popper perovskite films fabricated with a new deposition method. The analysis indexed all measured spots on the diffraction pattern which indicated high degree of crystallinity for these films and, crucially, perpendicular alignment of insulator organic spacer with respect to the electrode surface. 12.52% efficiency is achieved for this system with exceptionally high environmental stability, a major hurdle in utilizing perovskites in solar cells.
The same technique is applied in investigation of crystallinity of a blend of fluorinated and non-fluorinated small molecule donor compounds for bulk heterojunction solar cells. These molecules consist of benzodithiophene unit with two diketopyrrolopyrrole moieties. We show that 1:9 blend possesses highest degree of crystallinity. We attributed this effect to formation of C--H˙˙˙F hydrogen bonding, which improves intermolecular connectivity and enhances photoconductivity. The 1:9 ratio also exhibits the highest efficiency in solar cells as compared to blends with other ratios of constituents.
Notlar:
School code: 0163
Tüzel Kişi Ek Girişi:
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(690246.1) | 690246-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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