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Author ORCID Identifier

https://orcid.org/0000-0001-9717-0484

AccessType

Campus-Only Access for One (1) Year

Document Type

dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Chemical Engineering

Year Degree Awarded

2020

Month Degree Awarded

September

First Advisor

Christos Dimitrakopoulos

Second Advisor

Dimitrios Maroudas

Third Advisor

Dhandapani Venkataraman

Subject Categories

Engineering | Materials Science and Engineering | Semiconductor and Optical Materials

Abstract

Planar, p-i-n (inverted) hybrid organic-inorganic perovskite solar cells that use low-temperature, solution-processable charge-transport layers have garnered much attention due to their direct compatibility with flexible substrates and cost-effective roll-to-roll manufacturing. Nevertheless, this architecture has failed to repeatedly achieve the superior power conversion efficiencies frequently attained by its n-i-p counterpart. Additionally, the perovskite active layer has poor stability in the presence of prolonged light exposure, high temperatures, and moisture. In this study, we propose commercially viable strategies to improve the performance and stability of inverted methylammonium lead iodide perovskite solar cells. First, we show that a simple two-step method comprising evaporation-induced self-assembly of a lead iodide intermediate film coupled with the intermolecular exchange of methylammonium iodide can yield high-quality methylammonium lead iodide perovskite films on non-ideal surfaces. Complete inverted devices with the perovskite active layer formed via this method outperformed those devices with a perovskite layer produced using a conventional method. Second, we successfully replace the commonly used but environmentally unstable calcium-aluminum electrode with a more stable silver electrode in inverted perovskite devices via interfacial engineering without compromising device performance. By introducing a solution-processable, thickness-tolerant n-doped zwitterionic fulleropyrrolidine interlayer between the phenyl-C61-butyric acid methyl ester electron-transporting layer and the silver electrode, we successfully lower the work function of the silver and improve charge transport, which led to an increase in device performance compared to those devices with a calcium-aluminum electrode. Third, we examine the use of copper-based hole-transport materials in inverted perovskite solar cells as a replacement for the more commonly used but less stable poly(3,4-ethylenedioxythiophene) polystyrene sulfonate hole-transport material. We show that in most cases devices with a copper-based hole-transport material outperform those with a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate hole-transport material due to the additive benefits from all relevant film/material properties (i.e. morphology, optics, crystallinity/charge transport potential, and electronic band level alignment). Finally, we present a procedure to effectively transfer monolayer CVD graphene onto a perovskite surface without damaging or degrading the perovskite. We show that the incorporation of graphene significantly improves perovskite film and inverted device stability in the presence of moisture and heat without sacrificing the overall device performance.

DOI

https://doi.org/10.7275/18157052

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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