Inhomogeneous Biexciton Binding in Perovskite Semiconductor Nanocrystals Measured with Two-Dimensional Spectroscopy

Abstract

Perovskite semiconductor nanocrystals have emerged as an excellent family of materials for optoelectronic applications, where biexciton interaction is essential for optical gain generation and quantum light emission. However, the strength of biexciton interaction remains highly controversial due to the entangled spectral features of the exciton- and biexciton-related transitions in conventional measurement approaches. Here, we tackle the limitation by using polarization-dependent two-dimensional electronic spectroscopy and quantify the excitation energy-dependent biexciton binding energy at cryogenic temperatures. The biexciton binding energy increases with excitation energy, which can be modeled as a near inverse-square size dependence in the effective mass approximation considering the quantum confinement effect. The spectral line width for the exciton–biexciton transition is much broader than that for the ground state to exciton transition, suggesting weakly correlated broadening between these transitions. These inhomogeneity effects should be carefully considered for the future demonstration of optoelectronic applications relying on coherent exciton–biexciton interactions.

Resolving the Controversy in Biexciton Binding Energy of Cesium Lead Halide Perovskite Nanocrystals through Heralded Single-Particle Spectroscopy

“…A possible explanation for this broadening is the presence of multiple decay routes from the BX to the 1X state, possibly through thermally excited hot BX states which are close energetically to the lowest BX state. 31 , 34 We note that this is qualitatively different from observations in core/shell/shell CdSe/CdS/ZnS NCs. 16 , 17 However, II-VI semiconductor NCs feature more pronounced spectral diffusion compared to LHP NCs.…”

“… 30 Similar trends have been demonstrated for CsPbBr 3 at cryogenic temperatures using two-dimensional electron spectroscopy. 31 In addition, analyses of TA measurements by Ashner et al , that do not employ short-delay spectra, did not result in large positive values (but rather in small negative values of a few meV). 14 Together, these observations suggest that ε b measured when both excitons are at the band edge would be lower than that measured when the first exciton is still hot.…”

Perspective: multi-dimensional coherent spectroscopy of perovskite nanocrystals

“…Biexciton resonances in PNCs thus manifest in one-quantum spectra, specifically as negative peaks in the real-quadrature component [62]. This was observed in a recent study by Huang et al which applied MDCS to CsPbBr 3 PNCs in order to extract the biexciton binding energy as a function of nanocrystal size and temperature [61]. As shown in the real-quadrature one-quantum spectrum plotted in figure 7(a), a negative peak is observed that is red-shifted along the emission energy axis (relative to the positive single-exciton peak located at |ℏω τ | = |ℏω t |) by a value identical to the biexciton binding energy.…”

Resolving the controversy in biexciton binding energy of cesium lead halide perovskite nanocrystals through heralded single-particle spectroscopy

“…30 Similar trends have been demonstrated for CsPbBr 3 at cryogenic temperatures using two dimensional electron spectroscopy. 31 In addition, analyses of TA measurements by Ashner et al, that do not employ short-delay spectra, did not result in large positive values (but rather in small negative values of few meV). 16 Together, these observations suggest that ε b measured when both excitons are at the band edge would be lower than that measured when the first exciton is still hot.…”