Direct Bandgap Behavior in Rashba‐Type Metal Halide Perovskites. Issue 52 (29th October 2018)

• Record Type: Journal Article
• Authors: Richter, Johannes M.; Chen, Kai; Sadhanala, Aditya; Butkus, Justinas; Rivett, Jasmine P. H.; Friend, Richard H.; Monserrat, Bartomeu; Hodgkiss, Justin M.; Deschler, Felix
• Is Part Of: Advanced materials. Volume 30:Issue 52(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-10-29
• Subjects: direct bandgap -- perovskites -- semiconductors -- ultrafast photoluminescence; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.201803379
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: The generation and recombination of charge carriers in semiconductors through photons controls photovoltaic and light‐emitting diode operation. Understanding of these processes in hybrid perovskites has advanced, but remains incomplete. Using femtosecond transient absorption and photoluminescence, it is observed that the luminescence signal shows a rise over 2 ps, while initially hot photogenerated carriers cool to the band edge. This indicates that the luminescence from hot carriers is weaker than that of cold carriers, as expected from strongly radiative transitions in direct gap semiconductors. It is concluded that the electrons and holes show a strong overlap in momentum space, despite recent proposals that Rashba splitting leads to a band offset suppressing such an overlap. A number of possible resolutions to this, including lattice dynamics that remove the Rashba splitting at room temperature, and localization of luminescence events to length scales below 10 nm are considered. Abstract : The impact of Rashba effects in halide perovskites is still under debate. Using femtosecond transient absorption and photoluminescence, it is shown that luminescence from hot carriers is weaker than that of cold carriers, as expected from strongly radiative transitions in direct gap semiconductors. Several possible resolutions to this, including lattice dynamics that overcome Rashba splittings at room temperature are considered.