Perovskite
α-CsPbI3 nanocrystals (NCs) with a
high fluorescence quantum yield (QY) typically undergo a rapid phase
transformation to a low-QY δ-CsPbI3 phase, thus limiting
their optoelectronic applications. In this study, organic molecule
hexamethyldisilathiane (HMS) is used as a
unique surfactant to greatly enhance the stability of the cubic phase
of CsPbI3 NCs (HMS-CsPbI3) under ambient conditions.
The reaction kinetics of the phase transformation of CsPbI3 NCs are systemically investigated through in situ photoluminescence
(PL), X-ray diffraction, and transmission electron microscope (TEM)
measurements under moisture. The activation energy of HMS-CsPbI3 NCs is found to be 14 times larger than that of CsPbI3 NCs capped by olyelamine (OLA-CsPbI3 NCs). According
to density functional theory calculations, the bonding between HMS
and CsPbI3 NCs is stronger than that between OLA and CsPbI3 NCs, preventing the subsequent phase transformation. Our
study presents a clear pathway for achieving highly stable CsPbI3 NCs for future applications.