Halide perovskite nanocrystals with an ABX3 stoichiometry have become an increasingly interesting material system for optoelectronic applications due to their high fluorescence quantum yield, bandgap tunability through halide composition and now more recently due to the variation of sizes and dimensionalities accessible. However, there are still many open questions concerning the fundamental properties of perovskite nanocrystals especially pertaining to their recombination dynamics.
Here, we present results from optical spectroscopy experiments on hybrid organic-inorganic and all-inorganic nanoplatelets. In these studies, we were able to control the nanoplatelet thickness incrementally down to a single perovskite monolayer yielding absorption spectra similar to established two-dimensional semiconductors. In order to investigate the relaxation dynamics of photoexcited electron-hole pairs, we performed temperature-dependent transient absorption spectroscopy. We find that the carrier cooling behavior as well as the exciton formation dynamics depend on the thickness of the nanoplatelets. Moreover, we study the effect of nanoplatelet thickness and A-site cation on radiative and non-radiative recombination rates.