Abstract
Over the past decade, interest about metal halide perovskites has rapidly increased, as they can find wide application in optoelectronic devices. Nevertheless, although thermal evaporation is crucial for the development and engineering of such devices based on multilayer structures, the optical properties of thermally deposited perovskite layers (spontaneous and amplified spontaneous emission) have been poorly investigated. This paper is a study from a nano- to micro- and macro-scale about the role of light-emitting species (namely free carriers and excitons) and trap states in the spontaneous emission of thermally evaporated thin layers of CH3NH3PbBr3 perovskite after wet air UV light trap passivation. The map of light emission from grains, carried out by SNOM at the nanoscale and by micro-PL techniques, clearly indicates that free and localized excitons (EXs) are the dominant light-emitting species, the localized excitons being the dominant ones in the presence of crystallites. These species also have a key role in the amplified spontaneous emission (ASE) process: for higher excitation densities, the relative contribution of localized EXs basically remains constant, while a clear competition between ASE and free EXs spontaneous emission is present, which suggests that ASE is due to stimulated emission from the free EXs.
Highlights
Metal halide perovskite semiconductors have attracted extensive attention for their outstanding optoelectronic properties [1,2,3,4], such as high defect tolerance, long carrier lifetime and diffusion length, and tunable optical bandgap across the whole visible spectrum
Our experiment demonstrates that the control of the film morphology is crucial to determine the processes affecting the emission and, to control the emission properties of the active films
The role of free and localized EXs on the spontaneous optical emission properties in CH3 NH3 PbBr3 perovskite has been investigated at the micro-scale
Summary
Metal halide perovskite semiconductors have attracted extensive attention for their outstanding optoelectronic properties [1,2,3,4], such as high defect tolerance, long carrier lifetime and diffusion length, and tunable optical bandgap across the whole visible spectrum. Due to these features, perovskites found large application in photovoltaic cells [6,9], light-emitting diodes [10,11,12], and optically pumped lasers [13,14,15]. Perovskites found large application in photovoltaic cells [6,9], light-emitting diodes [10,11,12], and optically pumped lasers [13,14,15] For these devices, the study and individuation of the emission mechanisms are crucial issues to determine the channels for the photogenerated species loss, the spectral properties of the device emission, and the factors affecting the stimulated emission threshold. The correlation between emission mechanisms and processing conditions, as well as the material composition, environment [19], and photoinduced degradation [20], still represent open questions for these materials
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
