Abstract
Lead halide perovskite nanocrystals (PNCs) exhibit unique optoelectronic properties, many of which originate from a purported bright-triplet exciton fine-structure. A major impediment to measuring this fine-structure is inhomogeneous spectral broadening, which has limited most experimental studies to single-nanocrystal spectroscopies. It is shown here that the linearly polarized single-particle selection rules in PNCs are preserved in nonlinear spectroscopies of randomly oriented ensembles. Simulations incorporating rotational averaging demonstrate that techniques such as transient absorption and two-dimensional coherent spectroscopy are capable of resolving exciton fine-structure in PNCs, even in the presence of inhomogeneous broadening and orientation disorder.
Highlights
Semiconductor colloidal nanocrystals, called colloidal quantum dots, comprise a material platform that has sustained research interest over recent decades due to their numerous potential applications
We have presented the general framework for rotational-averaging a perturbative optical response, with applications to spectroscopy of randomly oriented ensembles of perovskite nanocrystals (PNCs)
Via simulations of transient absorption and 2DCS spectra, we showed that the linearly polarized single-particle selection rules of PNCs manifest in nonlinear spectroscopies of PNC
Summary
Semiconductor colloidal nanocrystals, called colloidal quantum dots, comprise a material platform that has sustained research interest over recent decades due to their numerous potential applications Their advantageous optical properties have found use in many areas such as displays [1], photovoltaics [2], and biological tagging [3]. Different to that of the original report of a bright-triplet exciton ground state (CsPbBr2 Cl) [6] This controversy both highlights our poor understanding of fine-structure in PNCs and emphasizes the need for new approaches to investigating their underlying physics. Exciton fine-structure of PNCs have, far, primarily been investigated via single-nanocrystal linear fluorescence spectroscopy to circumvent inhomogeneity [13]. Nanomaterials 2022, 12, 801 be used to measure properties of exciton fine-structure in PNCs even in the presence of dominant inhomogeneous broadening?
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