Electron–phonon interaction in efficient perovskite blue emitters

Abstract

Low-dimensional perovskites have-in view of their high radiative recombination rates-shown great promise in achieving high luminescence brightness and colour saturation. Here we investigate the effect of electron-phonon interactions on the luminescence of single crystals of two-dimensional perovskites, showing that reducing these interactions can lead to bright blue emission in two-dimensional perovskites. Resonance Raman spectra and deformation potential analysis show that strong electron-phonon interactions result in fast non-radiative decay, and that this lowers the photoluminescence quantum yield (PLQY). Neutron scattering, solid-state NMR measurements of spin-lattice relaxation, density functional theory simulations and experimental atomic displacement measurements reveal that molecular motion is slowest, and rigidity greatest, in the brightest emitter. By varying the molecular configuration of the ligands, we show that a PLQY up to 79% and linewidth of 20 nm can be reached by controlling crystal rigidity and electron-phonon interactions. Designing crystal structures with electron-phonon interactions in mind offers a previously underexplored avenue to improve optoelectronic materials' performance.

Broadband Extrinsic Self‐Trapped Exciton Emission in Sn‐Doped 2D Lead‐Halide Perovskites

“…2D perovskites, where bulky organic layers and inorganic layers are alternately and periodically arranged, feature natural quantum-well structures. [20,21] In these cases, severe structural distortion of metal halide octahedra is a common feature because of the size mismatch between organic and inorganic components, which results in potential fluctuations. [14][15][16] However, low photoluminescence quantum yields (PLQYs, typically < 1%) of 2D perovskites at room temperature is a bottleneck to achieving high-performance LEDs.…”

“…This quantum-well structure is regarded as promising LED emitters for decades. [22,23] Such fluctuations of potential within an inorganic layer of perovskite sometimes, but not always, [20,21] slow the diffusion of carriers or excitons, and consequently induce self-trapped excitons (STEs), which represents a type of bound states for efficient radiative recombination. [17] The low PLQYs may be attributed to insufficient confinement of Wannier type excitons within the inorganic layers [18] as suggested by the long charge-carrier/exciton diffusion length (60 nm).…”

“…[23,54,55] The presence of STEs is typically elusive because of their transient quasiparticle feature; they manifest themselves through a broadband luminescence. [21,57] To quantify the exciton-phonon interaction and the inhomogeneous line width due to structural fluctuations, we estimated the upper limit of homopolar phonon deformation potential (D CV ) by simply ignoring the contribution of acoustic phonon to the FWHM of PL spectra (Figure 3). Therefore, we can interpret such anomalous luminescence as extrinsic STEs emission, similar to the cases of II-VI semiconductor alloys.…”

Spintronics of Hybrid Organic–Inorganic Perovskites: Miraculous Basis of Integrated Optoelectronic Devices

“…Following a study of the electron‐phonon interaction effects on luminescence in 2D perovskites, Gong et al suggested in a recent work that reduction of the interactions was one viable way to create strong blue light emission . Three structures with organic cations were discussed; of these structures, C4 (CH 3 (CH 2 ) 3 ) and PhC2 (phenyl C 6 H 5 −(CH 2 ) 2 ) crystals showed sharp blue emissions, while the Ph (phenyl C 6 H 5 ) crystal was characterized by a broadband white light emission.…”

“…However, by using the excellent PL properties of HOPs, many blue LEDs have been proposed. In 2018, research revealed that strong electron‐phonon interactions reduce the PL . Based on this principle, researchers determined that the molecules in the brightest materials show the lowest and most rigid motions.…”