Metal halide perovskite nanocrystals (NCs), particularly CsPbBr3 (CPB) have emerged as promising materials for next-generation optoelectronic and photonic applications owing to their high photoluminescence quantum yield (PLQY), narrow emission linewidth, defect tolerance, and facile solution processability. In this work, we demonstrate Boron-Nitride (BN) assisted CPB nanocrystal system exhibiting enhanced optical performance, suppressed non-radiative losses, and improved carrier dynamics. BN nanosheets (BNNS) were incorporated during the synthesis process, where they act as effective nucleation and surface passivation centers, leading to the formation of highly emissive and stable CPB–BN nanocomposites.

Structural and morphological characterizations using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electron energy loss spectroscopy (EELS) confirm the successful incorporation of BN within the perovskite system while preserving the cubic crystal structure of CPB. Optical characterization shows a significant enhancement in emission properties, with the PLQY increasing from ~46% in pristine CPB NCs to ~85% in BN-assisted NCs. Time-resolved photoluminescence measurements further reveal prolonged carrier lifetimes and substantially suppressed non-radiative decay channels in the BN-treated samples. To understand the origin of the improved optical performance, femtosecond transient absorption spectroscopy (fs-TAS) was employed to probe ultrafast carrier dynamics. The BN-assisted NCs exhibit slower (~40%) multiexciton decay dynamics and reduced trion formation probability, indicating suppression of Auger-assisted ionization pathways. Fluence-dependent TAS measurements reveal an increase in biexciton lifetime together with a larger effective absorption cross-section, suggesting enhanced optical transition strength while simultaneously reducing non-radiative carrier loss pathways. These observations correlate well with the enhanced PLQY, and improved emission stability observed in steady-state and time-resolved measurements. The improved optical properties are attributed to effective surface passivation and interfacial interactions introduced by BNNS, which mitigate surface defect states and suppress carrier ionization processes. The combined enhancement in radiative recombination efficiency, environmental stability, and suppression of Auger-related losses makes the BN-assisted CPB system highly promising for high-performance light-emitting devices, low-threshold nanolasers, and stable single-photon emitters.