Stable biexcitons in two-dimensional metal-halide perovskites with strong dynamic lattice disorder

Abstract

With strongly bound and stable excitons at room temperature, single-layer, two-dimensional organic-inorganic hybrid perovskites are viable semiconductors for light-emitting quantum optoelectronics applications. In such a technological context, it is imperative to comprehensively explore all the factors -chemical, electronic and structural -that govern strong multi-exciton correlations.Here, by means of two-dimensional coherent spectroscopy, we examine excitonic many-body effects in pure, single-layer (PEA) 2 PbI 4 (PEA = phenylethylammonium). We determine the binding energy of biexcitons -correlated two-electron, two-hole quasiparticles -to be 44 ± 5 meV at room temperature. The extraordinarily high values are similar to those reported in other strongly excitonic two-dimensional materials such as transition-metal dichalchogenides. Importantly, we show that this binding energy increases by ∼ 25% upon cooling to 5 K. Our work highlights the importance of multi-exciton correlations in this class of technologically promising, solution-processable materials, in spite of the strong effects of lattice fluctuations and dynamic disorder. * FT and SN are to be considered first co-authors of this manuscript. †

Electron–Phonon Couplings Inherent in Polarons Drive Exciton Dynamics in Two-Dimensional Metal-Halide Perovskites

“…Furthermore, the perspective of distinct polaronic identity is supported by the observations that excitons A and B have distinct biexciton spectral structure. 8 Indeed, if distinct excitons are dressed differently by phonons, this difference should also be manifested in the resulting composite multi-particle binding energy, whereas a single exciton reflected in a vibronic progression should not display distinct binding energies by the phonon replicas.…”

Explaining observed stability of excitons in highly excited CdSe nanoplatelets

“…Figures 1, 3, and 4 show a dashed line marking the crossover X ↔ X 2 , from the exciton-dominated regime to the biexciton-dominated regime computed using Eqs. (8) and (9).…”

“…Biexcitons, that is, bound states of two excitons, have been extensively studied in the literature both theoretically and experimentally in various materials and under different conditions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. In particular, the study of the optical properties of excitons and biexcitons has received much attention in recent years, first in order to understand the underlying physics, and later towards possible new applications [16][17][18][19][20][21][22][23][24][25][26][27].…”

Band‐Edge Exciton Fine Structure and Exciton Recombination Dynamics in Single Crystals of Layered Hybrid Perovskites

“…Biexciton emission is evidenced at room temperature, with a binding energy of ≈45 meV and a lifetime of 80 ps. [20,23,24] The presence of these quasiparticles is exciting due to their unique role, leading to a better understanding of many body effects and their great promise for photonic applications. Transient photoluminescence resolves the low-lying dark exciton state, with a bright/dark splitting energy estimated to be 10 meV.…”

“…[21] This greatly enhanced exciton binding energy makes them particularly interesting for light-emitting applications. [20,23,24] The presence of these quasiparticles is exciting due to their unique role, leading to a better understanding of many body effects and their great promise for photonic applications. [20,23,24] The presence of these quasiparticles is exciting due to their unique role, leading to a better understanding of many body effects and their great promise for photonic applications.…”