Luisa Whittaker-Brooks, Professor of Chemistry, Kameron Hansen, post-doc in Whittaker-Brooks group, and John Colton from Brigham Young University worked together on Mechanistic origins of excitonic properties in 2D perovskites: Implications for exciton engineering, published by Matter on July 28, 2023.
Kameron Hansen, the postdoc research associate in the Luisa Whittaker-Brooks group, noted: “This was a project with a lot of moving parts, many collaborators, and many findings. Thinking back on it, we probed the two-dimensional perovskite sheets in nearly every way imaginable. We measured their response to light from 1 meter to 300 nanometers, tinkered with equations, looked at them under microscopes, ran theoretical calculations on supercomputers, and so on. For it all to tie together at the end, we had to maintain focus and “keep the main thing the main thing.” Hansen also stated: “Professor Whittaker-Brooks and John Colton from Brigham Young University gave me a lot of leeway and relentless support throughout this process. Working with the two of them on this project was among my life’s most fun and rewarding experiences.”
About the Project
Progress and Potential:
The properties of excitons underpin the absorption, emission, and energy transfer properties of quantum well systems. For GaAs-based quantum wells in the 1980s and 1990s, mapping the relationships between the exciton properties and the quantum well structure allowed for control of these optoelectronic properties, and ultimately led to the invention of blue light emitting diodes and the 2014 Nobel Prize in Physics. For quantum well systems of today such as 2D perovskites, there is a large variance in the reported values of the exciton’s properties, both measured and calculated. Here, we solve this issue by obtaining unambiguous measurements of the exciton properties. By repeating these measurements on a large number of structures, we map the relationships between exciton properties and the underlying quantum well structure. This allows us to determine the correct
theory for calculating exciton properties and ultimately enables the control of these properties.
Highlights:
• Direct measurements of Eb for 31 unique perovskite structures
• A strong correlation between Eb and Eg is identified and shown to be useful
• We find a superlattice model accurately describes the exciton properties
• Dielectric constants and theory show excitons are partially screened by phonons
eTOC blurb:
Exciton properties dictate the optical and electronic behavior of low-dimensional semiconductors; however, these properties have remained uncertain for 2D perovskites due to conflicting reports. This study uses spectroscopic tools to precisely measure exciton properties and theory to understand the observed trends. The reduced noise floor of our measurements renders clear a correlation between the band gap energy and exciton binding energy. Thus, traditional “band-gap engineering” also affects the strength of Coulomb interactions. Understanding these correlations allows for more informed engineering of low-dimensional semiconductors.