Colloidally synthesized cesium lead halide (CsPbX3;
X = Cl, Br, and I) perovskite nanocrystals (PNCs) often suffer from
poor ambient and environmental stability conditions, limiting their
practical applications. The commonly used surfactant oleylamine is
converted to the oleylammonium cation, which pulls out the halide
anion from the PNC surface, thus disrupting the structural integrity
and stability of the nanocrystal. We developed a simple, completely
amine-free colloidal synthesis with a hot injection method under open-atmospheric
conditions and introduced bromooctane as a bromine precursor to overcome
the above issues. These as-synthesized amine-free PNCs show a photoluminescence
quantum yield (PLQY) of around 60%, and the size of PNCs is ∼25
nm. Moreover, these amine-free PNCs were highly stable in colloidal
solutions and thin films for more than 5 months under ambient conditions,
with 66% of their initial PLQY. In addition, these PNCs show exceptional
stability under different environmental conditions, with 44% of the
initial PL even after water treatment under 6 h and 28% of the initial
PL under ethanol treatment of 120 min. Furthermore, they exhibit excellent
photostability for 96 h and retain 36% of their initial PL under ceaseless
UV light irradiation at 365 nm (8 W/cm2). In addition,
these PNCs have good stability upon heat treatment and maintain 34%
of the initial PL upon heating up to 90 °C. Finally, we fabricated
a green-emitting down-conversion light-emitting diode (LED) using
these amine-free PNCs. Therefore, we envision that these amine-free
CsPbBr3 PNCs are perhaps ideal candidates for perovskite-based
display applications.