Single-step, Atmospheric Pressure Chemical Vapor Deposition of Methylammonium Bismuth Iodide Thin Films

<p>Lead halide perovskites (CH₃NH₃PbI₃ and its variants) are promising solar cell absorber materials. Though the reported power conversion efficiencies of lead halide perovskite solar cells (up to 21%) are competitive with commercial silicon solar cells, lead toxicity in these perovskites present a challenge to further scale-up and eventual commercialization. Recently, bismuth (Bi³⁺) based organic halide perovskite has drawn attention as a substitution for lead-free perovskites, since it is a non-toxic 6p-block element, isoelectronic with Pb²⁺. Methylammonium bismuth iodide ((CH₃NH₃)₃Bi₂I₉) is reported for its non-toxic constituents and favorable optical band gap, thus making it a promising light absorber material. However, manufacturing ready, scale-up processes have not been developed for this compound and this presents a significant roadblock in integrating low-cost, non-toxic Bi-based perovskites into modern solar cell devices. Here, we report a single step, atmospheric pressure, chemical vapor deposition (CVD) process for (CH₃NH₃)₃Bi₂I₉. Atmospheric CVD addresses the need for rapid deposition across large area substrates, thus making the deposition of (CH₃NH₃)₃Bi₂I₉ thin films manufacturing-scalable. The precursors used are bismuth iodide (BiI₃) and methylammonium iodide (CH₃NH₃I) which are sublimated and subsequently deposited inside a tube furnace reactor with a well-controlled temperature profile. Extensive characterization is conducted via grazing incidence X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, UV-vis spectroscopy and variable temperature Hall measurements. Structural and electronic stability of (CH₃NH₃)₃Bi₂I₉ films in ambient are measured and degradation mechanisms elucidated.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering & Materials Science

Year dc:date.available

2017

Author dc:creator

• Chen, Xiao

Contributors dc:contributor

• Parag, Banerjee
• Bryce Sadtler Srikanth Singamaneni

• Methylammonium bismuth iodide
• chemical vapor deposition (CVD)
• Hall measurements
• lead-free photovoltaics
• Engineering
• Semiconductor and Optical Materials

Statement dc:rights

• I have not registered my thesis with the U.S. Copyright Office, and do not intend to.

Language dc:language

English (en)

Identifier

https://openscholarship.wustl.edu/eng_etds/251

OAI identifier oai:identifier

oai:openscholarship.wustl.edu:eng_etds-1253