Anharmonicity-driven Rashba co-helical excitons break quantum efficiency limitation

Abstract

Closed-shell light-emitting diodes (LEDs) suffer from the internal quantum efficiency (IQE) limitation imposed by optically inactive triplet excitons. Here we show an undiscovered emission mechanism of lead-halide-perovskites (LHPs) APbX${}_3$ (A=Cs/CN${}_2$H${}_5$; X=Cl/Br/I) that circumvents the efficiency limit of closed-shell LEDs. Though efficient emission is prohibited by optically inactive $J=0$ in inversion symmetric LHPs, the anharmonicity arising from stereochemistry of Pb and resonant orbital-bonding network along the imaginary A${}^{+}\cdots$X${}^{-}$ (T${}_{1u}$) transverse optical (TO) modes, breaks the inversion symmetry and introduces disorder and Rashba-Dresselhaus spin-orbit coupling (RD-SOC). This leads to bright co-helical and dark anti-helical excitons. Many-body theory and first-principles calculations affirm that the optically active co-helical exciton is the lowest excited state in organic/inorganic LHPs. Thus, RD-SOC can drive to achieve the ideal 50 $\%$ IQE by utilizing anharmonicity, much over the 25 $\%$ IQE limitation for closed-shell LEDs.

arXiv comment5 pages, 4 figures

References in corpus (14)

• New Perspectives for Rashba Spin-Orbit Coupling
• Bright triplet excitons in lead halide perovskites
• Local polar fluctuations in lead halide perovskite crystals
• Revealing the role of organic cations in hybrid halide perovskites CH3NH3PbI3
• Universal emission intermittency in quantum dots, nanorods, and nanowires
• Magnetic brightening and control of dark excitons in monolayer WSe2
• Role of Polar Phonons in the Photo Excited State of Metal Halide Perovskites
• Anharmonic vibrational properties in periodic systems: energy, electron-phonon coupling, and stress
• Acoustic Phonon Lifetimes Limit Thermal Transport in Methylammonium Lead Iodide
• Lattice thermal conductivities of two SiO${}_2$ polymorphs by first-principles calculation and phonon Boltzmann transport equation
• Band Topology, Orbital Phase Winding, and Selection Rules in Excitonic Physics in Two Dimensions
• Rashba-Dresselhaus Effect in Inorganic/Organic Lead Iodide Perovskite Interfaces
• Phonon-Driven Selective Modulation of Exciton Oscillator Strengths in Anatase TiO2 Nanoparticles
• Temperature dependence of the bulk Rashba splitting in the bismuth tellurohalides