Improving charge carrier dynamics in tin (II) sulfide through targeted defect engineering
Name
1057267966-MIT.pdf
Description
Full printable version
Size
23.84 MB
Format
Adobe PDF
Checksum (MD5)
fe0442e4d8393b00e218e429802a87cd
Author(s)
Polizzotti, Alex J
Advisor(s)
Tonio Buonassisi.
Date Issued
2018
Publisher
Massachusetts Institute of Technology
Abstract
Tin sulfide is an emerging material for photovoltaics, with the potential for highthroughput manufacturing to combat climate change by displacing fossil fuel generation. However, device efficiencies for SnS have plateaued at below 5% efficiency, making them as yet insufficient for commercial production. Low minority carrier lifetimes of <100 ps have been shown to be the root cause of this low performance, and carrier lifetimes >1 ns are predicted to enable >10%-efficient devices. In this thesis work, I employed defect modeling to identify the most recombination-active point defects: the extrinsic Fe[subscript Sn], Co[subscript Sn], and Mo[subscript Sn] and the intrinsic V[subscript S]. I grew SnS single crystals and demonstrated that by suppressing these defects during growth, I could improve minority carrier lifetime to >1 ns. I built a unique, highly customized close-spaced sublimation furnace to translate these learnings to device-relevent thin films. By designing a system for metal-free, sulfur-rich growth at high temperature, I was able to achieve >10 ns carrier lifetimes in SnS thin films. I fabricated initial devices with this high-purity material. While none of these devices exceed the record efficiencies, they are primarily limited by poor device construction and a resulting low fill factor, and further improvements are expected to unlock the full potential of this new, improved SnS material.
Description
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 145-151).
Subjects
Mechanical Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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