Setting an Upper Bound to the Biexciton Binding Energy in CsPbBr₃ Perovskite Nanocrystals

Abstract

Cesium lead halide perovskite nanocrystals are promising emissive materials for a variety of optoelectronic applications. To fully realize the potential of these materials, we must understand the energetics and dynamics of multiexciton states which are populated under device relevant excitation conditions. We utilized time-resolved and spectrally-resolved photoluminescence studies to investigate the biexciton binding energy as well as a red-shifted emission feature previously reported under high-flux excitation conditions. We determine that this red-shifted emission feature can be ascribed to sample sintering induced by air-exposure and high-flux irradiation. Furthermore, we determine that the biexciton binding energy at room temperature is at most ±20 meV, providing a key insight toward understanding many-body interactions in the lead halide perovskite lattice.

Domain‐Size‐Dependent Residual Stress Governs the Phase‐Transition and Photoluminescence Behavior of Methylammonium Lead Iodide

“…The crystalline state of MAPbI 3 perovskite differs as a result of the specific growth technique selected for the final optoelectronic device, ranging from homogeneous bulk single‐crystals to inhomogeneous PC thin films or low‐dimensional partially oriented structures (e.g., nanowires, quantum dots, and highly ordered crystals). [ 29–33 ] To investigate the structural differences between these crystalline states, we selected three archetypal platforms: PC, HOC, and SC MAPbI 3 perovskites fabricated through spin‐coating, [ 17,34 ] temperature‐gradient‐assisted solidification, [ 35 ] and inverse temperature crystallization processes, [ 36 ] respectively. Figure A shows photographs of the three structures and the top‐views of scanning electron microscopy images, whereas the inset histograms present their domain‐size distributions.…”

Guidelines for the characterization of metal halide nanocrystals

“…The study of the physical properties of MH NCs is a vivid field of research relying on various continuous-wave and time-resolved optical spectroscopies performed under controlled temperature [55][56][57][58][59][60] and environmental conditions [61][62][63] at both the ensemble and the single-particle level (Figure 4) [64][65][66][67]. This enables us to build a comprehensive photophysical picture including the bandgap energy [20,27], the emission spectrum and its excitonic versus defect/dopantbased contributions [6,[68][69][70][71][72], the exciton [73] and biexciton binding energies [74], and the rates of radiative and nonradiative processes in single NC and ensembles [75][76][77] and in hybrid architectures [78][79][80][81][82], as well as the extent of blinking processes and single-photon emission properties [64][65][66][67] (Figure 4). Overall, this information offers design guidelines for the engineering of perovskite NCs with optical properties tailored for specific applications.…”

“…Therefore, excessively energetic excitation might lead to underestimation of the PLQY with respect to band-edge-excitation conditions [63]. Time-resolved spectroscopies are the techniques of choice to investigate the dynamics of the carriers [85], trapping and transfer, the emission kinetics, as well as the exciton [73] and biexciton binding energies [74]. These include time-resolved PL and transient absorption that provide complementary evaluation of the oscillator strength and the time evolution of the excited-state population.…”

Heralded Spectroscopy Reveals Exciton–Exciton Correlations in Single Colloidal Quantum Dots

“…More indirect methods to probe the BX state rely on power-dependent measurement of photoluminescence (PL) (either in a time-resolved or quasi-continuous-wave manner) 20 , 22 , 23 , 27 or of transient absorption. 21 , 28 While careful modeling and analysis of these measurements provided important spectroscopic information, it has often led to large variance in BX binding energies measured in different studies.…”