Abstract
The established theory of a two-dimensional (2D) Wannier exciton in a uniform electric field is used to analyze the electroabsorption response of an archetypal 2D metal halide perovskite (MHP), phenethylammonium lead iodide. The high level of agreement between the electroabsorption simulation and measurement allows for a deepened understanding of the redshift of exciton energy, according to the quadratic Stark effect, and the continuum wave function leaking, according to the Franz-Keldysh effect. We find the field dependency of each of these effects to be rich with information, yielding measurements of the exciton Bohr radius, transition dipole moment, polarizability, and reduced effective mass of the exciton. Most importantly, the band-gap energy and exciton binding energy are unambiguously determined with 1σ variance of 4 meV. The high precision of these new measurement methods opens the opportunity for determining the influence of chemical and environmental factors on the optoelectronic properties of MHPs, which would enable the fabrication of highly efficient and reproducible light-harvesting and light-emitting optoelectronic devices.
- Received 21 September 2021
- Revised 22 December 2021
- Accepted 2 February 2022
DOI:https://doi.org/10.1103/PRXEnergy.1.013001
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Metal-halide perovskites are an exciting class of materials with attractive fundamental physics as well as promise for application in solar cells, with efficiencies similar to those of silicon-based systems. To optimize the optical and electronic properties, understanding of electron states must advance and measurement of their energies must be precise. Here, measurement precision of the binding energy of electron states is increased by an order of magnitude, from ~40 meV to ~4 meV. Atomic layers of metal-halide perovskites are deposited on an array of gold electrodes, which allows for large electric fields to be applied parallel to the layered structure. Charged particles strongly absorb at a preferred photon energy, which shifts according to the Stark effect under applied electric fields; this energy shift is rich with information about the electron states. This high-precision measurement method is promising for understanding various influences on electron states, and thereby gaining control of important properties in the engineering of next-generation optoelectronic devices.
