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Ultrafast spectroscopy of metal halide perovskites and III-V semiconductors
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Monti, Maurizio (2020) Ultrafast spectroscopy of metal halide perovskites and III-V semiconductors. PhD thesis, University of Warwick.
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WRAP_Theses_Monti_2020.pdf - Submitted Version - Requires a PDF viewer. Download (3543Kb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b3492284~S15
Abstract
A key phenomenon to improve even further the efficiency of photovoltaic technology is hot carrier dynamics: the possibility of harvesting hot, energetic carriers in photovoltaics could increase the efficiency of such devices beyond the Shockley-Queisser limit.
In this thesis advances in the understanding of hot carrier dynamics in metal halide perovskite semiconductors (MHP) are reported: the influence of the composition on the hot carrier cooling process was investigated by means of optical pump terahertz probe spectroscopy (OPTP) and transient absorption spectroscopy (TA). In particular the role of the metal in controlling the electron-phonon coupling and phonon-phonon coupling was studied.
A new phenomenological model aimed at describing the cooling dynamics of hot carriers is introduced, and its parameter linked to the microscopical physical processes underlying energy relaxation.
A fully inorganic tin-based perovskite semiconductor is studied using OPTP and the hot carrier cooling time connected to the first stage of cooling is measured, compared to the prototypical III-V semiconductor GaAs, and linked to the Fröhlich electron-LO phonon interaction. The influence of the bandstructure on the dynamics is also assessed.
A series of mixed lead-tin perovskites with controlled Pb/Sn ratio is investigated by both OPTP and TA spectroscopy. The numerical outcome of the two techniques is investigated and the differences linked to the different physical processes the two techniques probe, helping clarify discrepancies that appeared in previous works on the subject. The influence of the metal fraction on the cooling dynamic is also established, and linked to the modification of the electron-phonon and phonon-phonon interaction caused by alloying.
Finally the simpler, narrow-gap semiconductor InSb is studied for the first time via terahertz cyclotron spectroscopy. The effective mass of InSb was measured during the cooling of hot carriers towards the band edge, finding that the change in effective mass during this process is indeed measurable and can be described by a simple model assuming a nonparabolic band dispersion.
These findings suggest possible new directions for the design and implementation of future of future semiconductor materials and devices with optimised carrier cooling profiles.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QC Physics Q Science > QD Chemistry T Technology > TA Engineering (General). Civil engineering (General) |
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Library of Congress Subject Headings (LCSH): | Metal oxide semiconductors, Hot carriers, Perovskite, Metal halides, Optical spectroscopy, Flash photolysis | ||||
Official Date: | April 2020 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Lloyd-Hughes, James | ||||
Format of File: | |||||
Extent: | xvi, 144 leaves : illustrations (chiefly colour) | ||||
Language: | eng |
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