We show here the first colloidal
synthesis of double perovskite
Cs2AgInCl6 nanocrystals (NCs) with a control
over their size distribution. In our approach, metal carboxylate precursors
and ligands (oleylamine and oleic acid) are dissolved in diphenyl
ether and reacted at 105 °C with benzoyl chloride. The resulting
Cs2AgInCl6 NCs exhibit the expected double perovskite
crystal structure, are stable under air, and show a broad spectrum
white photoluminescence (PL) with quantum yield of ∼1.6 ±
1%. The optical properties of these NCs were improved by synthesizing
Mn-doped Cs2AgInCl6 NCs through the simple addition
of Mn-acetate to the reaction mixture. The NC products were characterized
by the same double perovskite crystal structure, and Mn doping levels
up to 1.5%, as confirmed by elemental analyses. The effective incorporation
of Mn ions inside Cs2AgInCl6 NCs was also proved
by means of electron spin resonance spectroscopy. A bright orange
emission characterized our Mn-doped Cs2AgInCl6 NCs with a PL quantum yield as high as ∼16 ± 4%.
We report a one-step
synthesis of halide perovskite nanocrystals
embedded in amphiphilic polymer (poly(acrylic acid)-
block
-poly(styrene), PAA-
b
-PS) micelles, based on injecting
a dimethylformamide solution of PAA-
b
-PS, PbBr
2
, ABr (A = Cs, formamidinium, or both) and “additive”
molecules in toluene. These bifunctional or trifunctional short chain
organic molecules improve the nanocrystal–polymer compatibility,
increasing the nanocrystal stability against polar solvents and high
flux irradiation (the nanocrystals retain almost 80% of their photoluminescence
after 1 h of 3.2 w/cm
2
irradiation). If the nanocrystals
are suspended in toluene, the coil state of the polymer allows the
nanocrystals to undergo halide exchange, enabling emission color tunability.
If the nanocrystals are suspended in methanol, or dried as powders,
the polymer is in the globule state, and they are inert to halide
exchange. By mixing three primary colors we could prepare stable,
multicolor emissive samples (for example, white emitting powders)
and a UV-to-white color converting layer for light-emitting diodes
entirely made of perovskite nanocrystals.
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