Developing next generation, non-toxic, inorganic materials for photovoltaics and thin-film transistors

The focus of this thesis is on developing two next-generation inorganic materials for thin-film device applications, namely photovoltaics and thin-film transistors. Both of these device applications are crucial in today’s technology-based society with photovoltaics enabling sustainable generation of electricity whilst advancements in thin-film transistors allow for development of low-power, efficient electronic devices. BiOI, a non-toxic, perovskite-inspired material is investigated for photovoltaics (PVs) whilst Cu₂O, with a reasonably high predicted hole mobility is developed for *p*-type thin-film transistors (TFTs). These novel materials are fabricated with scalable processing techniques which enable lower manufacturing costs and improve energy efficiency. In the first results chapter, the suitability of non-toxic BiOI as a photovoltaic material is investigated. Dense BiOI films grown by thermal chemical vapour deposition (CVD) incorporated into an all-inorganic ITO/NiO_*x*/BiOI/ZnO/Al stack demonstrate high external quantum efficiencies (80% at 450 nm wavelength). However, the 1.9 eV band gap of BiOI is not matched to terrestrial solar spectra; the PVs achieve 1.8% power conversion efficiency. Owing to improved spectral matching with indoor light spectra, BiOI devices improve in efficiency to 4.37% under 1000 lux white light emitting diode indoor illumination, and millimetre-area BiOI devices are sufficient to power novel carbon nanotube inverters. The factor limiting further efficiency gains is downwards band-bending at the BiOI/NiO_*x* interface owing to NiO_*x* having a lower work function. In the second chapter, MoS₂ is investigated as an alternative to NiO_*x* where the work function of MoS₂ is tuned through oxygen plasma treatment to increase its work function. The experimental examination of defect tolerance of BiOI is conducted in chapter three. BiOI films are vacuum-annealed to induce surface composition changes. Large changes in surface atomic fractions (reduction in iodine and bismuth by 40% and 5% respectively, and increase in oxygen by >45%) are observed. These significant changes do not affect the electronic and optoelectronic properties, in contrast to traditional covalent semiconductors. The applicability of low-temperature (≤ 200 °C) atmospheric pressure spatial atomic layer deposited (AP-SALD) Cu₂O for use in *p*-type TFTs is explored in chapter four. The performance of AP-SALD Cu₂O is comparable to atomic layer deposition (ALD) grown Cu₂O with an I_*ON*/I_*OFF* ratio of 10³, and field-effect mobility between 10^-4 - 10^-3 cm²·V^-1·s^-1, illustrating the potential of AP-SALD grown films for integration with flexible substrates.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Huq, Tahmida

Advisor dc:contributor.advisor

• Driscoll, Judith

• atmospheric pressure spatial atomic layer deposition
• bismuth oxyiodide
• copper oxide
• indoor photovoltaics
• nanotechnology
• perovskite-inspired materials
• photovoltaics
• thin-film transistors

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/775cc775-d4be-4642-aeaa-495ed37c0e86/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.101974

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/358203