Solution-processable semiconductor lasers have been a long-standing challenge for next-generation displays, light sources, and communication technologies. Metal halide perovskites, which combine the advantages of inorganic and organic semiconductors, have recently emerged not only as excellent candidates for solution-processable lasers but also as potential complementary gain materials for filling the “green gap” and supplement industrial nanolasers based on classic II–VI/III–V semiconductors. Numerous perovskite lasers have been developed successfully with superior performance in terms of cost-effectiveness, low threshold, high coherence, and multicolor tunability. This mini review surveys the development, current status, and perspectives of perovskite lasers, categorized into thin film lasers, nanocrystals lasers, microlasers, and device concepts including polariton and bound-in-continuum lasers with a focus on material fundamentals, cavity design, and low-threshold devices in addition to critical issues such as mass fabrication and applications.

The hybrid nature and soft lattice of organolead halide perovskites render their structural changes and optical properties susceptible to external driving forces such as temperature and pressure, remarkably different from conventional semiconductors. Here, we investigate the pressure-induced optical response of a typical two-dimensional perovskite crystal, phenylethylamine lead iodide. At a moderate pressure within 3.5 GPa, its photoluminescence red-shifts continuously, exhibiting an ultrabroad energy tunability range up to 320 meV in the visible spectrum, with quantum yield remaining nearly constant. First-principles calculations suggest that an out-of-plane quasi-uniaxial compression occurs under a hydrostatic pressure, while the energy is absorbed by the reversible and elastic tilting of the benzene rings within the long-chain ligands. This anisotropic structural deformation effectively modulates the quantum confinement effect by 250 meV via barrier height lowering. The broad tunability within a relatively low pressure range will expand optoelectronic applications to a new paradigm with pressure as a tuning knob.

The fast-growing field of atomically thin semiconductors urges a new understanding of two-dimensional excitons, which entirely determine their optical responses. Here, taking layered lead halide perovskites as an example of unconventional two-dimensional semiconductors, by means of versatile optical spectroscopy measurements, we resolve fine-structure splitting of bright excitons of up to ∼2 meV, which is among the largest values in two-dimensional semiconducting systems. The large fine-structure splitting is attributed to the strong electron–hole exchange interaction in layered perovskites, which is proven by the optical emission in high magnetic fields of up to 30 T. Furthermore, we determine the g-factors for these bright excitons as ∼+1.8. Our findings suggest layered lead halide perovskites are an ideal platform for studying exciton spin-physics in atomically thin semiconductors that will pave the way toward exciton manipulation for novel device applications.

No abstract

Up-conversion photoluminescence (UCPL) refers to the elementary process where low-energy photons are converted into high-energy ones via consecutive interactions inside a medium. When additional energy is provided by internal thermal energy in the form of lattice vibrations (phonons), the process is called phonon-assisted UCPL. Here, we report the exceptionally large phonon-assisted energy gain of up to ~8k B T (k B is Boltzmann constant, T is temperature) on all-inorganic lead halide perovskite semiconductor colloidal nanocrystals that goes beyond the maximum capability of only harvesting optical phonon modes. By systematic optical study in combination with a statistical probability model, we explained the nontrivial phonon-assisted UCPL process in perovskites nanocrystals, where in addition to the strong electronphonon (light-matter) coupling, other nonlinear processes such as phonon-phonon (matter-matter) interaction also effectively boosts the upconversion efficiency.