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Influence of Electron Transport Layer on the Charge Carriers in Halide Perovskite Solar Cells

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Thesis embargoed until 6th December 2026(10.28 MB)

Date

2025

Authors

Yusuf, Abubakar Sadiq

Supervisor

Chen, Zhan
Ramezani, Maziar
Fiedler, Holger

Item type

Thesis

Degree name

Doctor of Philosophy

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Publisher

Auckland University of Technology

Abstract

Perovskite solar cells (PSCs) have emerged as highly promising contenders for next-generation photovoltaic technology, thanks to their exceptional power conversion efficiency (PCE), low-cost production methods, and customizable optical and electronic characteristics. This combination of features positions PSCs as strong candidates to replace or complement traditional silicon-based solar cells. Despite their rapid progress, PSCs face critical challenges that hinder their large-scale commercialization, with stability and efficient charge transport being among the most pressing issues. Addressing these challenges is crucial for realizing the complete potential of PSCs in sustainable, long-term renewable energy applications. The electron transport layer (ETL) plays a critical role in determining the performance of PSCs by facilitating the extraction and transfer of photogenerated electrons from the perovskite absorber layer to the electrode. Among several ETL materials, tin dioxide (SnO2) has emerged as a prominent choice owing to its superior optical transparency, exceptional chemical and thermal stability, and wide bandgap. These characteristics result in minimal parasitic absorption and high electron mobility, rendering SnO2 an ideal interface for effective charge extraction and transport in PSC designs. Moreover, SnO2 exhibits significant resistance to photodegradation, which is a crucial advantage for enhancing the operational stability of PSCs under continuous illumination. Despite its strengths, the performance of SnO2 may be limited by its moderate electrical conductivity, which can impede charge collection and increase recombination losses at the ETL/perovskite interface. To address these issues, it is essential to understand the interplay between intrinsic defects and charge transport mechanisms in SnO2. Its n-type conductivity, mainly driven by oxygen vacancies, can be finely tuned through doping and defect engineering. In this study, noble gas ion beam modification was demonstrated to effectively reduce the resistivity of colloidal SnO2. Ar+ implantation followed by post-annealing led to enhanced conductivity through increased carrier concentration and partial defect healing. Additionally, antimony (Sb+) implantation showed superior results compared to xenon (Xe+), providing better conductivity and thermal stability. While a slight reduction in optical transparency was observed for both Sb+ and Xe+ implantations, Sb+ consistently outperformed Xe+ in dopant activation and defect passivation. Notably, the thermal stability of Sb+-implanted films was confirmed through repeated annealing cycles and long-duration heating tests, showing minimal degradation in conductivity or structural integrity. These results align with prior studies suggesting that antimony doping can enhance both carrier transport and durability in SnO2-based films, making them robust candidates for long-term photovoltaic operation.

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http://hdl.handle.net/10292/19276

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Doctoral Theses