Chemistry Reference
In-Depth Information
spherical and 30 nm in diameter. Substitution of OAm for a non-
coordinating solvent resulted in the chalcopyrite phase of CuInSe
2
, as did the
use of elemental selenium or selenourea.
A similar reaction was used to grow tetragonal or cubic crystalline
Cu
1.5
InSe
2
nanowires using metal nanoparticle catalysts.
9
The stoichiometry
of the
nal product varied, but it was clearly the ternary compound. In this
example, In(O
2
CCH
3
)
3
, Cu(O
2
CCH
3
), oleic acid and TOP were mixed and
heated to 100
C, followed by cooling to room temperature and mixing with
TOPSe. This precursor solution was injected into a freshly prepared solution
of Au/Bi core/shell particles in TOP at 300
C, resulting in solution
d
n
1
y
4
n
g
|
2
-
solid (SLS) catalytic growth of CuInSe
2
wires. Changing the order of addition/
temperature also yielded solid-state by-products, such as Cu
3
Se
2
and Cu
3
P
depending upon reaction conditions. In this report, the CuInSe
2
wires
showed an absorption onset at
ca.
1200 nm.
Most of the above routes to CuInSe
2
did not report the optical properties in
any depth. A report by Allen and Bawendi
10
did, however, report impressive
optical properties for spherical Cu
-
liquid
-
In
-
Se QDs with a chalcopyrite structure,
a
er suggesting TOPSe was not ideally suited as a chalcogen source while
referring to previous mechanistic studies. Particles of CuIn
5
Se
8
were ob-
tained by the dispersion of CuI and InI
3
in a mixture of TOP and OAm at
between 280
C and 360
C, followed by the injection of Se(SiMe
3
)
2
and
growth at 210
C for a short period of time. The particles clearly exhibited
band edge emission towards the red/near infrared end of the visible spec-
trum, with excitonic features present in the optical spectra and quantum
yields up to 25%. Changing the metal precursors from the iodide salt to the
chloride salt resulted in a di
.
ering stoichiometry, which could be tuned from
CuIn
1.5
Se
3
to CuIn
2.3
Se
4
by varying the reaction temperature (injection
temperature of 350
C and growth of temperature of 280
C for CuIn
1.5
Se
3
;
injection temperature of 280
C and growth of temperature of 210
C for
CuIn
2.3
Se
4
). Overall, emission from QDs of Cu
Se could be tuned
between 650 and 975 nm. Replacing CuI with AgI resulted in AgInSe
2
QDs
which emitted between
ca.
625 nm and 650 nm, with a maximum quantum
yield of 15%.
The related ternary compound system, copper
-
In
-
-
-
de, was pre-
pared in a similar manner. Cu-oleate and indium oleate (prepared by the
reaction of the metal chlorides and sodium oleate) were mixed in OAm with
dodecanethiol, then heated to between 230
C and 250
C for up to 1 hour.
11
By varying reaction temperature and time, di
indium
sul
erent sizes and shapes of
nanoparticles could be prepared, from
ca.
30
-
50 nm
'
nanoacorns
'
with
clearly visible regions of Cu
2
S and In
2
S
3
to
'
larva
'
-shaped particles up to
110 nm in length. X-ray di
raction (XRD) showed the particles were
composed of Cu
2
S and In
2
S
3
rather than the solid solution of copper and
indium sul
de; the reaction product could be thought of more as a hetero-
structure than a true ternary compound. A similar method using a non-
coordinating solvent has been used, resulting in CuInS
2
;
3
a mixture of the
metal salts and dodecanethiol in octadecene (ODE) was heated to 240
C
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