Colloidal lead halide perovskites (LHP) nanocrystals (NCs) are popular light-emissive materials for optoelectronic devices, of interest for LEDs, LCDs, lasers and quantum light sources. Most studies on LHP NCs focus on relatively large NCs exceeding 10 nm in size, exhibiting weak to no quantum confinement effects. Recently, we showed that perovskite quantum dots (QDs) can be synthesized using a newly developed synthesis route, resulting in perovskite QDs that are tunable between 3 and 13 nm range.[1] Further exploring the tunability of these QDs, we extend the emission of these materials through doping, as well as by coupling these QDs to anchored luminescent dyes.[2,3] First, we demonstrate the synthesis of size-tunable spheroidal CsPbCl₃:Mn²⁺ QDs, which can be obtained by a water–hexane interfacial combined anion and cation exchange strategy starting from CsPbBr₃ QDs.[2] The size dependence observation of the manganese PL efficiency and the slow ET rate suggest that Mn²⁺ mainly gets incorporated at the QD’s surface, highlighting the importance of strategies chosen for the incorporation of Mn²⁺ into perovskite QDs.

In a second approach to tune and extend the perovskite QD´s emission, we combined the perovskite QDs with dye molecules, make hybrid QD-dye systems that exhibit efficient ET from the QDs to the dye molecules.[3] With most QDs, ET usually proceeds through Förster resonance energy transfer (FRET), which requires significant spectral overlap between the QD emission and dye absorbance, and large oscillator strengths of those transitions which severely limits the choice of suitable dyes. As the perovskite QDs do not require passivating inorganic shells for bright emission, we can attach dye molecules directly to their surface, making ET mechanisms beyond FRET accessible. With the CsPbBr₃-ATTO610 QD-dye system we achieved efficient ET from CsPbBr₃ QDs to dyes with dimethyl iminium binding groups. The close binding of dyes to the CsPbBr₃ surface facilitates spatial wavefunction overlap, resulting in efficient ET from CsPbBr₃ to dyes with bright emission from the dye molecules, even with minimal spectral overlap. With steady-state and time-resolved photoluminescence experiments, we show that the ET proceeds via the Dexter exchange-type mechanism which significantly improves the tuneability of such QD-dye systems, and opening avenues for QD-molecule hybrids in a wide range of such as lighting applications