Shen, Kai;
(2021)
Solution-Processed Perovskite Photodetectors.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Photodetectors enable conversion from light signals to electrical signals and are widely used in both the civil and military field for applications such as missile guidance, optical communication, imaging and biomedical sensing. Although various semiconductors have been employed in photodetectors, their high cost and complexity of fabrication have hindered their further development. Recently, perovskites have attracted substantial interest due to their impressive optoelectronic properties, including tuneable bandgaps, large absorption coefficient, long diffusion length and high carrier mobility. However, perovskites are generally not stable when exposed to ambient air, which seriously degrades the device performance. In this thesis, all-inorganic perovskite quantum dot (QD)-based photodetectors are investigated to enhance the material quality, device photoresponse and environmental stability. Three efficient strategies are developed to optimise the material film morphology and optical properties, as well as light confinement. I also managed to develop perovskite QD detectors on flexible substrates. Firstly, caesium lead bromide (CsPbBr3) QDs were optimised by blending ZnO nanoparticles (NPs), and further employed in a heterostructured photodetector. The as-fabricated device exhibited an improved photoresponse, including a 10-fold improved responsivity (0.4 mA W-1) and a short response time of 73.5 ms, as well as an excellent air stability (~ 7 month) due to the enhanced film morphology and optical properties after the decoration of ZnO NPs. Secondly, CsBr/KBr additives and a photovoltaic architecture were developed to further boost the device performance. An enhanced surface morphology and crystal quality with reduced defects were achieved by CsBr/KBr mediation. The resulting flexible photodetectors exhibited a better photoresponse, good flexibility and outstanding electrical stability. Specifically, this optimized photodetector showed a high responsivity of 10.1 A W-1, a large detectivity approaching 1014 Jones, and an on/off ratio around 104. In addition to the material optimisations, anodic aluminium oxide plasmonic structures were adopted with control of geometry and decoration of metallic NPs in the perovskite photodetectors, which enabled efficient light transmission and collection, and resulted in a 40-fold enhancement in device photoresponse. In the future, I will continue to focus on material and structural optimisations to develop high-performance and stable optoelectronics. In addition, perovskite-based focal plane arrays have great potential to be investigated.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Solution-Processed Perovskite Photodetectors |
| Event: | UCL (University College London) |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10130595 |
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