Highly anisotropic single perovskite nanorods (NRs) offer polarized emission and high photoluminescence (PL) quantum yields, making them promising candidates for quantum light sources. Here, we make use of the quantum-confined Stark effect (QCSE) to tune the optical response of individual CsPbBr₃ NRs with well-defined orientation relative to an external electric field. PL spectroscopy reveals a reversible QCSE, allowing to extract the polarizability and to prove the existence of a permanent dipole moment. A clear relation between field-induced emission energy shift, spectral line broadening, and PL intensity quenching is found. Interestingly, our study reveals a correlation between polarizability and zero-field PL intensity, hinting towards a screening effect of the passivating ligands. These findings offer a strategy for tuning perovskite NC emission, e.g., with respect to a cavity mode, in a well-defined way.

Magic-sized (CdSe)₁₃ clusters (MSCs) represent a material class at the boundary between molecules and quantum dots that exhibit a pronounced and well separated excitonic fine structure. The characteristic photoluminescence is composed of exciton bandgap emission and a spectrally broad mid-gap emission related to surface defects. Here, we report on a thermally activated energy transfer from fine-structure split exciton states to surface states by using temperature dependent photoluminescence excitation spectroscopy. We demonstrate that the broad mid-gap emission can be suppressed by a targeted Mn-doping of the MSC leading to the characteristic orange luminescence of the ⁴T₁ → ⁶A₁ Mn²⁺ transition. The energy transfer to the Mn²⁺ states is found to be significantly different than the transfer to the surface defect states, as the activation of the dopant emission requires a spin-conserving charge carrier transfer that only dark excitons can provide.