Resonantly Pumped Bright-Triplet Exciton Lasing in Cesium Lead Bromide Perovskites

Abstract

The surprising recent observation of highly emissive triplet-states in lead halide perovskites accounts for their orders-of-magnitude brighter optical signals and high quantum efficiencies compared to other semiconductors. This makes them attractive for future optoelectronic applications, especially in bright low-threshold nanolasers. While nonresonantly pumped lasing from all-inorganic lead-halide perovskites is now well-established as an attractive pathway to scalable low-power laser sources for nano-optoelectronics, here we showcase a resonant optical pumping scheme on a fast triplet-state in CsPbBr 3 nanocrystals. The scheme allows us to realize a polarized triplet-laser source that dramatically enhances the coherent signal by 1 order of magnitude while suppressing noncoherent contributions. The result is a source with highly attractive technological characteristics, including a bright and polarized signal and a high stimulated-to-spontaneous emission signal contrast that can be filtered to enhance spectral purity. The emission is generated by pumping selectively on a weakly confined excitonic state with a Bohr radius ∼10 nm in the nanocrystals. The exciton fine-structure is revealed by the energy-splitting resulting from confinement in nanocrystals with tetragonal symmetry. We use a linear polarizer to resolve 2-fold nondegenerate sublevels in the triplet exciton and use photoluminescence excitation spectroscopy to determine the energy of the state before pumping it resonantly.

1-nm linewidth room temperature single-photon source from optical microcavity-embedded CsPbI3 perovskite quantum dots

“…This results in bright triplet states-the only known example of a material with this property-which can help explain the up-to 1000× brighter PL intensity observed in PQDs compared with other semiconductors. A Rashba-type effect due to symmetry perturbation inverts the energies of singlet and triplet exciton states and lifts the fine structure degeneracy to reveal the ultra-narrow linewidths within the fine structure in the orthorhombic and tetragonal phases of the crystal 21,28 , but not in the orthogonal phase where the splitting is degenerate. Different PQDs exhibit different decay times, where the variations in lifetime can be attributed to differences in the sizes of the nanocrystals, hence different quantum confinement energies 30 .…”

“…The noteworthy optical performance can in part be attributed to the presence of fast, opticallyactive, triplet states (Fig 1b), present uniquely in lead halide perovskites 21,28,29 . Spin-forbidden triplet transitions delay PL emission, but in these systems they become dipole-allowed due to unusually strong spin-orbit coupling from heavy Pb ions.…”

Highly stable and controllable lasing actions from PVDF encapsulated CsPbBr3 perovskite microcrystals

“…Halide perovskite (HP) materials exhibit excellent optical properties for flexible and low-cost photonic devices including lasers, [1][2][3] light-emitting diodes, and photodetectors, etc. [4][5][6][7][8][9][10][11] HP crystals, such as micro prisms, nanowires, and microspheres, manifest low threshold and high Q factor lasing actions based on the Fabry-Pe ´rot (F-P) [12][13][14] resonance or the whisperinggallery-mode (WGM) resonance. 15,16 Perovskite WGM lasing was first reported in the hexagonal MAPbI 3Àx Cl x MAPbI 3Ày Br y microrods prepared by the chemical vapor deposition (CVD) method with a threshold of 37 mJ cm À2 at room temperature.…”

Ultranarrow Line Width Room-Temperature Single-Photon Source from Perovskite Quantum Dot Embedded in Optical Microcavity

“…The noteworthy optical performance can in part be attributed to the presence of fast, optically active, triplet states (Figure b), present uniquely in lead halide perovskites. ,, Spin-forbidden triplet transitions delay PL emission, but in these systems, they become dipole-allowed due to unusually strong spin–orbit coupling from heavy Pb ions. This results in bright triplet states (the only known example of a material with this property) which can help explain the bright PL intensity observed in PQDs.…”

“…This results in bright triplet states (the only known example of a material with this property) which can help explain the bright PL intensity observed in PQDs. A Rashba-type effect due to symmetry perturbation inverts the energies of singlet and triplet exciton states and lifts the fine structure degeneracy to reveal the ultranarrow line widths within the fine structure in the orthorhombic and tetragonal phases of the crystal, , but not in the orthogonal phase where the splitting is degenerate. Different PQDs exhibit different decay times, where the variations in lifetime can be attributed to differences in the sizes of the nanocrystals, hence different quantum confinement energies …”