Tuning the Colloidal Softness of CsPbBr₃ Nanocrystals for Homogeneous Superlattices

Abstract

Perovskite nanocrystal superlattices (NC SLs), made from millions of ordered crystals, support collective optoelectronic phenomena. Coupled NC emitters are highly sensitive to the structural and spectral inhomogeneities of the NC ensemble. Free electrons in scanning electron microscopy (SEM) are used to probe the cathodoluminescence (CL) properties of CsPbBr3 SLs with a ∼20 nm spatial resolution. Correlated CL-SEM measurements allow for simultaneous characterization of structural and spectral heterogeneities of the SLs. Hyperspectral CL mapping shows multipole emissive domains within a single SL. Consistently, the edges of the SLs are blue-shifted relative to the central domain by up to 65 meV. We discover a relation between NC building block colloidal softness and the extent of the CL shift. Residual uniaxial compressive strains accompanying SL formation are contributors to these emission shifts. Therefore, precise control over the colloidal softness of the NC building blocks is critical for SL engineering.

Bright Innovations: Review of Next-Generation Advances in Scintillator Engineering

“…Lead halide perovskites, and in particular CsPbBr 3 , show giant oscillator strength and photoluminescence lifetimes that are an order of magnitude shorter than typical semiconducting nanocrystals, promising for ultrafast scintillation and detection . Also, CsPbBr 3 nanocrystals have bright tunable narrow emission , and reach near-unity quantum yield without thick inorganic shelling, indicating defects tolerance, unlike traditional semiconducting nanocrystals . Unfortunately, these materials experience strong self-absorption due to their small Stokes shift, and recently our group published a report on how composition tuning in double perovskites allows regulating Stokes shift by moving absorption and/or emission bands .…”