Resonant free-carrier absorption in 2D hybrid organic-inorganic perovskites: The Rashba effect or small polarons?
Abstract
The Rashba effect, which shifts the conduction band extremum from wavevector k = 0 to |k| = k0 ≠ 0 with an energy gain of ER, has been frequently invoked to explain outstanding optoelectronic properties in hybrid organic-inorganic perovskites (HOIPs). For two-dimensional (2D) layered HOIPs, the only direct experimental evidence of the Rashba effect to date is resonant free-carrier absorption (FCA), which has been attributed to direct optical transition between the Rashba subbands at |k| = k0 ≠ 0 with photon energy ℏω = 4ER. Here, we show that in layered perovskites, small polarons induced by a strong short-range coupling between electrons and optical phonons can also give rise to a resonant FCA at ℏω = 4Eb, with Eb being the polaron binding energy. The Rashba effect- and small-polaron-induced resonant FCA responses can be distinguished via an applied electric field, which moves the resonance peak to a higher or lower photon energy in the former but splits the peak into two in the latter, suggesting that electric-field-modulated FCA can help prove and quantify the Rashba effect and/or small polarons in layered perovskites.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 26, 2019
- Source ID
- 10.1063/1.5127459
Entities
People
- Zhi-Gang
Organizations
- Army Research Office
- Washington State University