Transient Photophysics of Bismuth Halide Semiconductors for Optoelectronic Applications
type: CreativeWork
description: This thesis describes a series of spectroscopic studies of three different semiconductors based on bismuth halides in order to discover their fundamental photophysical properties. The materials investigated — the double perovskite Cs2AgBiBr6, bismuth iodide, and bismuth oxyiodide — have all been demonstrated in thin film photovoltaic devices fabricated at low temperatures. Propelled by the success of lead halide perovskites, this work forms part of the search for defect tolerant, non-toxic and stable materials for next-generation solar cells. I use transient absorption spectroscopy to show that the charge carrier lifetime in Cs2AgBiBr6 thin films is 1.4 μs. This is significantly longer than previous estimates based on time-resolved photoluminescence measurements, which measure the radiatively decaying carriers, but is a less sensitive probe of the high proportion of carriers which recombine non-radiatively. I propose a radiative recombination mechanism via defects, based on the detection of mid-gap electronic states in the transient absorption spectra. Coherent phonon transients are also measured on ultrafast timescales showing strong electron-phonon coupling in the material, which may contribute to the slow recombination in this material. The recombination dynamics of excitons in the layered material bismuth iodide, BiI3, are investigated using temperature dependent photoluminescence and transient absorption. I show that coupling to interlayer and intralayer phonon modes strongly affects the direct exciton decay pathway through scattering and modulation of the band gap energy. In a single crystal of BiI3, the room temperature exciton lifetime is 72 ns, which indicates this material’s potential for photovoltaics if the defects in thin films can be passivated. I show that the excited states of thin films of layered bismuth oxyiodide, BiOI, have a great degree of energetic disorder, most likely due to the presence of self-trapped excitons and defect states. Transient …
abstract: This thesis describes a series of spectroscopic studies of three different semiconductors based on bismuth halides in order to discover their fundamental photophysical properties. The materials investigated — the double perovskite Cs2AgBiBr6, bismuth iodide, and bismuth oxyiodide — have all been demonstrated in thin film photovoltaic devices fabricated at low temperatures. Propelled by the success of lead halide perovskites, this work forms part of the search for defect tolerant, non-toxic and stable materials for next-generation solar cells. I use transient absorption spectroscopy to show that the charge carrier lifetime in Cs2AgBiBr6 thin films is 1.4 μs. This is significantly longer than previous estimates based on time-resolved photoluminescence measurements, which measure the radiatively decaying carriers, but is a less sensitive probe of the high proportion of carriers which recombine non-radiatively. I propose a radiative recombination mechanism via defects, based on the detection of mid-gap electronic states in the transient absorption spectra. Coherent phonon transients are also measured on ultrafast timescales showing strong electron-phonon coupling in the material, which may contribute to the slow recombination in this material. The recombination dynamics of excitons in the layered material bismuth iodide, BiI3, are investigated using temperature dependent photoluminescence and transient absorption. I show that coupling to interlayer and intralayer phonon modes strongly affects the direct exciton decay pathway through scattering and modulation of the band gap energy. In a single crystal of BiI3, the room temperature exciton lifetime is 72 ns, which indicates this material’s potential for photovoltaics if the defects in thin films can be passivated. I show that the excited states of thin films of layered bismuth oxyiodide, BiOI, have a great degree of energetic disorder, most likely due to the presence of self-trapped excitons and defect states. Transient …
author: Eyre, Lissa
language: eng
keywords: spectroscopy, optoelectronics, semiconductors, bismuth halide
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/499c8a02-cdc2-416e-a049-611c304893b4/download
license: http://purl.org/NET/rdflicense/allrightsreserved
date published: 2020-07-13
date modified: 2026-07-22T22:24:27Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.76129