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Three dimensional photonic crystals for optoelectronic applications

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Title: Three dimensional photonic crystals for optoelectronic applications
Authors: Poussin, David
Item Type: Thesis or dissertation
Abstract: Inverse opals are nano-structures with three dimensional periodicity, which confers them a control on the light passing through them. The light can be forbidden to exist within the structure, giving a physical e ect known as optical band-gap, which is the analogue of the electronic band-gap observed in semiconductors materials. For these reasons, these structures are part of a larger class of materials, called photonic crystals. In addition of the light control, inverse-opal structures o er a large surface area in an organised way, which makes them advantageous in specialised devices. Due to the complex fabrication process needed to produce high-quality inverse opal, only a limited amount of work has been done on their integration in optoelectronic devices. To complete this gap, this thesis aims to produce inverse opals made from new materials, for use in optoelectronic devices, such as solar cells and light emitting diodes. This thesis is divided in 5 results chapters, as described hereafter. Chapter 3 details the fabrication procedures developed to obtain reproducible inverse opals on a large scale. The structures are made by using an opal template made of polystyrene nanoparticles, which shows excellent optical properties, which is then in ltrated with precursors. In chapter 4, a new concept for solar cell architecture is proposed, with the use of a uorine tin oxide inverse opal as a three dimensional electrode, to optimise the charge collection, and lead halide perovskite as an absorbing layer. The in ltration of lead halide perovskite inside the inverse opal is very challenging due to the complex crystallisation of this material. A partial in ltration can be obtained with an optimised deposition method, and working solar cells have been made with this architecture. Work to prepare large-scale crack-free inverse opal made of uorine tin oxide is described chapter 5. Due to the high reactivity of the precursors used to make this material, a di erent approach of in ltration is made, with the synthesis and use of nano-crystals of this material. The structures made in this section show a great decrease in the amount of cracks, as well as very good periodicity. In chapter 6, a novel architecture for a light-emitting diode is proposed, which makes use of the optical properties of the inverse opal to sharpen the emission spectrum. A method to homogeneously coat the inverse opal by sol-gel has been optimised, and a standard OLED has been made, to con rm the choice of materials. The structures are simulated with a nite-di erence-time-domain (FDTD) code, in order to study their optical properties. To nish, the work in chapter 7 reports the creation of very large scale structures of 15x15cm2, which show good optical effects.
Content Version: Open Access
Issue Date: Apr-2020
Date Awarded: Oct-2020
URI: http://hdl.handle.net/10044/1/83286
Copyright Statement: Creative Commons Attribution NonCommercial Licence
Supervisor: McLachlan, Martyn Louis Maxime
Sponsor/Funder: European Commission
Department: Materials
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Materials PhD theses

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