Spontaneous emission

Physics

Geology

Nanotechnology

Laser

Optics

Oceanography

Engineering

Perovskite (structure)

Scintillator

Composite material

Halide

Light-emitting diode

Exciton

Inorganic chemistry

Chemistry

Thin film

Materials science

Substrate (aquarium)

Lasing threshold

Quantum mechanics

Diode

Radioluminescence

Photoluminescence

Chemical engineering

Optoelectronics

Caesium

Wavelength

Nanometre

Detector

Advanced Materials

Cesium lead halide perovskites are of interest for light‐emitting diodes and lasers. So far, thin‐films of CsPbX 3 have typically afforded very low photoluminescence quantum yields (PL‐QY &lt; 20%) and amplified spontaneous emission (ASE) only at cryogenic temperatures, as defect related nonradiative recombination dominated at room temperature (RT). There is a current belief that, for efficient light emission from lead halide perovskites at RT, the charge carriers/excitons need to be confined on the nanometer scale, like in CsPbX 3 nanoparticles (NPs). Here, thin films of cesium lead bromide, which show a high PL‐QY of 68% and low‐threshold ASE at RT, are presented. As‐deposited layers are recrystallized by thermal imprint, which results in continuous films (100% coverage of the substrate), composed of large crystals with micrometer lateral extension. Using these layers, the first cesium lead bromide thin‐film distributed feedback and vertical cavity surface emitting lasers with ultralow threshold at RT that do not rely on the use of NPs are demonstrated. It is foreseen that these results will have a broader impact beyond perovskite lasers and will advise a revision of the paradigm that efficient light emission from CsPbX 3 perovskites can only be achieved with NPs.

Room‐Temperature Stimulated Emission and Lasing in Recrystallized Cesium Lead Bromide Perovskite Thin Films