Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.763844
Title: Effects of low temperature and structure on the photophysics of alkylammonium lead halide semiconductors
Author: Booker, Edward Peter
ISNI:       0000 0004 7653 4324
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2019
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Abstract:
This thesis investigates some of the physics of semiconducting low-dimensional structures at low temperatures, as well as investigating the effects of defects on low-dimensional structures and magnetic fields on charge recombination in organic photovoltaics (OPVs). The applications of the systems studied vary from photodetectors, to LEDs, lasers and solar cells. We synthesised Cs2CuCl4 and CsCuCl3 nanoparticles. By varying the ratio of coordination solvents in the synthesis we can control the composition and morphologies of the fabricated nanoparticles, including dots, rods and wires. These nanocrystals showed broadband green emission upon excitation with sub-300 nm radiation, which we showed was due to emission from an intra-band Cu(II) defect. We also fabricated a variety of alkylammonium lead iodide materials. We found that hexylammonium lead iodide and dodecylammonium lead iodide emit broadband red light at low temperatures due to a Frenkel defect (f-centre). Additionally, we see evidence of biexciton emission in dodecylammonium lead iodide films at high excitation densities below temperatures of 225 K. The films in this study were seen to adopt two coexistent phases of dodecylammonium lead iodide, both a monoclinic P121/a structure and an orthorhombic Pbca structure, at room temperature. These films were used as the gain medium in a biexciton vertical cavity laser. This device was constructed from a distributed Bragg reflector coated with dodecylammonium lead iodide, a poly(methylmethacrylate) spacer layer, and an evaporated silver mirror. The onset of lasing was seen at 5.6 × 1018 excitations/cm3 at 75 K. Finally, the modulation of open-circuit voltage and short-circuit current by applied magnetic field in OPV devices made from PIDTPhanQ and PC(71)BM was investigated. We saw that magnetic fields influenced the recombination of charge-transfer (CT) states, and simulations indicated that the formation of CT states had a significant contribution from the bimolecular recombination of free charges. The simulations also showed that singlet CT state lifetimes were much smaller than triplet CT state lifetimes.
Supervisor: Greenham, Neil C. Sponsor: EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.763844  DOI:
Keywords: Perovskite ; Laser ; Colour Centre ; Nanoparticle ; XRD
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