- Title
- Towards upscaling the perovskite solar cell
- Creator
- Lian, Camilla
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2021
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Producing simple, high performance and cost-effective devices for solar energy harvesting are key requirements for next-generation photovoltaics. Perovskite solar cells have experienced unprecedented progress in device efficiencies since their discovery in 2009, and their precursor material abundance and versatility make them a sustainable option for use in emerging photovoltaic systems. Optimisation of the perovskite solar cell involves choosing the best device architecture, including improving the film morphology and crystal/defect chemistry of the light absorber. Additionally, research into scalable fabrication pathways is essential to progress the technology to large-scale applications. This thesis presents research into solution-based fabrication methods of perovskite films, primarily focusing on scalable immersion treatments on small substrates, and introduces some alternative charge transport layers for optimising stability, charge-carrier extraction, and substrate-to-perovskite connectivity. Tandem application of perovskite films with crystalline Si devices provides a potential direction for commercialisation of the technology. By Cs+ substitution with formamidiniumbased perovskites, optically tuneable perovskite films may be produced by varying the ratio of I− and Br− within the perovskite crystal. However, incorporation of Cs+ into the perovskite lattice provides some challenges related to intercalation chemistry and solubility of Cs-halide salts in solvents that are typically used for perovskite fabrication. Defining an appropriate pathway for Cs+ incorporation by using a scalable fabrication method thus formed an important goal for this thesis. By employing a sequential deposition pathway, the introduction of perovskite components may be separated into several steps. This allows for different fabrication methods to be combined, which may address some of the challenges associated with Cs+ inclusion. In this work, the best results are obtained when the Cs+ is included as part of a PbX2 (X = I−, Br−) precursor film, before the perovskite is converted by scalable chemical bath deposition (Chapter 4). This afforded a champion device efficiency of >14% for a perovskite solar cell with a tandem-suitable bandgap of ~1.7 eV, achieved with molar precursor contents of 0.1 Cs+, 0.6 I−, and 0.4 Br−. To achieve a fully scalable fabrication pathway, chemical vapour deposition (CVD) could form part of or the entire perovskite fabrication process. Precursor incorporation of Cs+ may be realised by a vapour deposition process, where developing alternative precursor salts could lead to optimisation of the crystal formation and film morphology. A preliminary investigation into the fabrication and behaviour of Cs+ and Pb+ pivalate salts is provided due to their beneficial sublimation behaviour at lower temperatures. In addition, a spin-coated pivalate precursor is tested with perovskite conversion in a chemical bath. The results suggest a need for optimisation of the precursor deposition to afford a uniform film with the right morphology for perovskite conversion, which may be provided by CVD in future work. During the sequential perovskite fabrication processes, a need was identified for mechanical substrate scaffolding to avoid film delamination in the chemical bath conversion step. For this purpose, hydrothermally deposited SnO2 nanostructures are investigated for use as a bifunctional scaffold and electron transport layer. The sequentially fabricated perovskite films developed in Chapter 4 were deposited on top of the nanostructures, which exhibit different sizes and morphology based on hydrothermal reaction timeframes between 6-24 hrs. Short reaction timeframes (~6 hrs), affording small structures on a pre-deposited SnO2 colloid layer, resulted in improved device performance. However, a slight misalignment observed between the energy levels of the perovskite and SnO2 layers resulted in worse performing devices compared to what is typically seen with the use of mesoporous TiO2. The nanostructured SnO2 layers were therefore not explored further for application in the sequentially fabricated perovskite solar cells. The last study in this thesis provides a preliminary investigation into the fabrication and characterisation of Fe(II)-ligand complexes for use as hole transport materials in perovskite solar cells (Chapter 7). Promising results are reported for Fe(II)(4,4’-dihydroxy-bipyridine)3 (Fe(DOHbpy)3), showing a power conversion efficiency of 7.7%, using a Fe(DOHbpy)3 concentration of only 5 mg mL−1. This topic was expanded on in later research, which is provided as a second author published journal article in Appendix 1.
- Subject
- perovskite; photovoltaics; thin-film; energy; solar
- Identifier
- http://hdl.handle.net/1959.13/1506245
- Identifier
- uon:55834
- Rights
- Copyright 2021 Camilla Lian
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 9 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 279 KB | Adobe Acrobat PDF | View Details Download |