Surface energy level and ambient photoemission characterisation of metals and semiconductors for optoelectronic and sensing applications

  • David Eric James Webster

Student thesis: Doctoral Thesis (PhD)

Abstract

The accurate measurement of energy levels within metals and semiconductors is essential to informing the design of future device architectures. Within this thesis, the Kelvin probe is used to provide highly accurate characterisation of energy levels within a wide range of materials, from elementary metals such as copper and zinc to multi-halide perovskites and polymer blends.

A combination of ambient photoemission spectroscopy, contact potential difference and absorption spectroscopy is used to characterise a series of multi-halide perovskite thin films for applications in indoor light harvesting, with a halide stoichiometry – iodine:bromine:chlorine – of 2.6 : 0.2 : 0.2 determined to give the best results, before being applied to experimentally confirm DFT calculations of an intercalated bromine perovskite, the first of its kind to be reported in literature, with experimental values agreeing well with the modelled perovskite.

Brass was studied as a model material for the mixing of materials into one sample, before this model was applied to polymer:fullerene blends of P3HT:PC₆₁BM and MEH-PPV:PC₆₁BM, with an overall aim of producing a model which could be applied to additional blends of organic molecules. The results showed that blends cannot always be treated as a simple superposition of components, with crystallinity of one or more component molecules showing a tendency to skew the results, necessitating corrective factors.

Finally, the surface scanning method of contact potential difference was used, complemented by surface-enhanced Raman spectroscopy, to develop a Kelvin probe-based sensor which was able to detect PFAS molecules reliably down to environmentally relevant concentrations.
Date of Award30 Jun 2025
Original languageEnglish
Awarding Institution
  • University of St Andrews
SupervisorGraham Turnbull (Supervisor), Ifor Samuel (Supervisor) & Iain Baikie (Supervisor)

Keywords

  • Contact potential difference
  • Ambient photoemission spectroscopy
  • Organic semiconductors
  • Perovskite semiconductors
  • Trace chemical sensing

Access Status

  • Full text embargoed until
  • 16 May 2026

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