Metal halide perovskite nanocrystals (PNCs) have emerged as a versatile class of materials owing to their outstanding optoelectronic properties and facile solution processability. Achieving high crystallinity and long-term stability is essential for advancing their integration into high-performance optoelectronic devices. In our recent work, we have established a series of synthesis strategies to obtain phase-stable, low-defect PNCs across diverse compositions, including Pb-based, Sn–Pb alloyed, Sn-based, and lead-free double perovskite systems[1-12]. Comprehensive photophysical investigations—spanning steady-state and ultrafast spectroscopies—have enabled us to elucidate photoexcited carrier dynamics such as hot-carrier relaxation, carrier extraction, and recombination pathways, thereby clarifying the structure–property–device relationships in these materials[5,7,11].

A major focus has been the identification and engineering of defects that critically limit the performance of Sn–Pb alloyed and Sn-based PNCs[8-10]. Temperature-dependent static and transient absorption spectroscopy allows us to disentangle static disorder (defects and impurities) from dynamic disorder arising from carrier–phonon coupling. We find that static disorder primarily introduces band-tail defect states, whereas dynamic disorder governs bandgap renormalization; together, they dictate fast carrier trapping and slower band-to-band recombination dynamics. Atomic-resolution STEM imaging and first-principles calculations further reveal that antisite defects generate deep-level trap states, serving as dominant nonradiative pathways. In parallel, we elucidated oxygen-driven and solvent-driven oxidation mechanisms of Sn, which severely impede the development of Sn–Pb and Sn-based PNCs.

To overcome these limitations, we devised a synergistic antioxidation strategy combining tri-n-octylphosphine (TOP) with micron-sized Sn powder. This approach effectively suppresses Sn(IV) formation, reduces defect trapping, and alleviates lattice distortion, enabling high-symmetry α-phase CsSnI₃ nanocrystals with ultralong carrier lifetimes (>200 ns). When applied to Sn–Pb alloyed PNCs, this strategy increased the photoluminescence quantum yield to 35% and extended carrier lifetimes by nearly two orders of magnitude[8].

These insights provide critical design principles for developing highly luminescent, low-toxicity Sn-based perovskite nanocrystals, and they open promising pathways toward their practical implementation in LEDs, solar cells, and other next-generation optoelectronic technologies.