Comparative optical characterization of CsPbBr3 quantum dots and CVD-grown CsPbBr3 microplates

Abstract

We systematically investigate the influence of morphology on exciton dynamics and bandgap behavior in all-inorganic CsPbBr₃ nanostructures by comparing colloidal quantum dots (QDs) and chemical vapor deposition (CVD)-grown microplates. Despite their identical composition, the two forms exhibit markedly different optical characteristics due to variations in dimensionality, crystallinity, and surface/interface conditions. Steady-state and temperature-dependent photoluminescence (PL) spectroscopy, supported by structural analysis, reveals a quantum confinement-induced blueshift and shorter exciton lifetime in the QDs, whereas the microplates display sharper emission, longer carrier lifetimes, and enhanced coupling with lattice phonons. Notably, temperature-induced PL shifts are deconvoluted into thermal expansion and electron–phonon interaction components using a one-oscillator model, showing a stronger thermomechanical response in the microplates due to substrate-induced strain and larger volume. Interestingly, the exciton binding energy is higher in the microplates (46.3 meV) than in the QDs (33.9 meV), likely due to surface defects and dielectric screening effects in the ligand-capped QDs. These findings clarify the distinct role of morphology in governing exciton recombination, phonon coupling, and optical stability, offering new insights for the rational design of perovskite-based optoelectronic devices.