Enhanced Contribution of Biexciton‐Mediated Decay Kinetics in Perovskite Nanocrystals Via Sequential Ultrafast Excitation

Controlling the temporal and kinetic statistics of excitons in semiconductor nanocrystals is important for understanding how multiexcitonic processes emerge in ultrafast excited‐state dynamics under low‐fluence conditions. Under conventional single‐pulse excitation, the Poissonian nature of exciton generation limits the manifestation of biexciton‐mediated processes in the observed kinetics at low fluence. Here, we demonstrate a sequential ultrafast excitation scheme in CsPbBr 3 nanocrystals that reshapes the temporal excitation context without increasing the total excitation fluence. By partitioning the excitation into two time‐delayed pulses within the exciton lifetime, residual excitons from the first pulse interact with newly generated excitations from the second pulse, increasing the relative kinetic weighting of the biexciton‐mediated fast decay channel in the measured early‐time response. Transient absorption measurements reveal a pronounced acceleration of the early‐time decay kinetics under sequential excitation, reflecting an increase of ~50% in the relative fast‐component weighting associated with biexciton‐mediated recombination, compared to single‐pulse excitation at the same total fluence (μ 1 + μ 2 = μ). This strategy provides a spectroscopically well‐defined way to enhance the observable kinetic contribution of biexciton‐mediated decay, highlighting temporal excitation structuring as a useful experimental handle for probing multiexcitonic kinetics in quantum‐confined materials.