We report experiments on bilayer light emitting diodes made with organically capped CdSe(CdS) core/shell type semiconductor nanocrystals and an electroluminescent (EL) semiconducting polymer [poly(p-phenylenevinylene) or PPV]. The devices emit from red to green with external quantum efficiencies of up to 0.22% at brightnesses of 600 cd/m2 and current densities of 1 A/cm2. They have operating voltages as low as 4 V and lifetimes under constant current flow of hundreds of hours. Most of these numbers are significant improvements over similar devices made with CdSe nanocrystals. The devices show either nanocrystal-only EL or a combination of nanocrystal and PPV EL, depending on nanocrystal layer thickness. The nanocrystal EL is dependent on nanocrystal size. Some devices show a voltage dependent spectral output. The spectral output is consistent with a field dependent electron range in the nanocrystal layer limited by carrier trapping.

1.
V. L.
Colvin
,
M. C.
Schlamp
, and
A. P.
Alivisatos
,
Nature (London)
370
,
354
(
1994
).
2.
B. O.
Dabbousi
,
M. G.
Bawendi
,
O.
Onitsuka
, and
M. F.
Rubner
,
Appl. Phys. Lett.
66
,
1316
(
1995
).
3.
Y.
Yang
,
J.
Huang
,
S.
Liu
, and
J. C.
Shen
,
J. Mater. Chem.
7
,
131
(
1997
).
4.
L.
Spanhel
,
M.
Haase
,
H.
Weller
, and
A.
Henglein
,
J. Am. Chem. Soc.
109
,
5649
(
1987
).
5.
A. R.
Kortan
,
R.
Hull
,
R. L.
Opila
,
M. G.
Bawendi
,
M. L.
Steigerwald
,
P. J.
Carroll
, and
L. E.
Brus
,
J. Am. Chem. Soc.
112
,
1327
(
1990
).
6.
C. F.
Hoener
,
K. A.
Allan
,
A. J.
Bard
,
A.
Campion
,
M. A.
Fox
,
T. E.
Mallouk
,
S. E.
Webber
, and
J. M.
White
,
J. Phys. Chem.
96
,
3812
(
1992
).
7.
W. L.
Wilson
,
P. F.
Szajowski
, and
L. E.
Brus
,
Science
262
,
1242
(
1993
).
8.
A.
Mews
,
A.
Eychmuller
,
M.
Giersig
,
D.
Schooss
, and
H.
Weller
,
J. Phys. Chem.
98
,
934
(
1994
).
9.
M.
Danek
,
K. F.
Jensen
,
C. B.
Murray
, and
M. G.
Bawendi
,
Chem. Mater.
8
,
173
(
1996
).
10.
M. A.
Hines
and
P.
Guyot-Sionnest
,
J. Phys. Chem.
100
,
468
(
1996
).
11.
A.
Mews
,
A. V.
Kadavanich
,
U.
Banin
, and
A. P.
Alivisatos
,
Phys. Rev. B
53
,
13
242
(
1996
).
12.
Y.
Tian
,
T.
Newton
,
N. A.
Kotov
,
D. M.
Guldi
, and
J. H.
Fendler
,
J. Phys. Chem.
100
,
8927
(
1996
).
13.
X.
Peng
,
M. C.
Schlamp
,
A. V.
Kadavanich
, and
A. P.
Alivisatos
,
J. Am. Chem. Soc.
119
,
7019
(
1997
).
14.
N. C.
Greenham
,
R. H.
Friend
, and
D. D. C.
Bradley
,
Adv. Mater.
6
,
491
(
1994
).
15.
A. R.
Brown
,
N. C.
Greenham
,
J. H.
Burroughes
,
D. D. C.
Bradley
,
R. H.
Friend
,
P. L.
Burn
,
A.
Kraft
, and
A. B.
Holmes
,
Chem. Phys. Lett.
200
,
46
(
1992
).
16.
R. N.
Marks
,
D. D. C.
Bradley
,
R. W.
Jackson
,
P. L.
Burn
, and
A. B.
Holmes
,
Synth. Met.
55–57
,
4128
(
1993
).
17.
P. W. M.
Blom
,
M. J. M.
de Jong
, and
M. G.
van Munster
,
Phys. Rev. B
55
,
R656
(
1997
).
18.
C. C.
Wu
,
J. K. M.
Chun
,
P. E.
Burrows
,
J. C.
Sturm
,
M. E.
Thompson
,
S. R.
Forrest
, and
R. A.
Register
,
Appl. Phys. Lett.
66
,
653
(
1995
).
19.
H.
Vestweber
,
H.
Bassler
,
J.
Gruner
, and
R. H.
Friend
,
Chem. Phys. Lett.
256
,
37
(
1996
).
20.
P. M. Borsenberger and D. S. Weiss, Organic Photoreceptors for Imaging Systems (Dekker, New York, 1993).
21.
H.
Antoniadis
,
M. A.
Abkowitz
, and
B. R.
Hsieh
,
Appl. Phys. Lett.
65
,
2030
(
1994
).
22.
A. H.
Nethercot
,
Phys. Rev. Lett.
33
,
1088
(
1974
).
23.
L. E.
Brus
,
J. Chem. Phys.
79
,
5566
(
1983
).
24.
N. C.
Greenham
,
S. C.
Moratti
,
D. D. C.
Bradley
,
R. H.
Friend
, and
A. B.
Holmes
,
Nature (London)
365
,
628
(
1993
).
25.
J. C.
Scott
,
J. H.
Kaufman
,
P. J.
Brock
,
R.
DiPietro
,
J.
Salem
, and
J. A.
Goitia
,
J. Appl. Phys.
79
,
2745
(
1996
).
26.
J. R.
Sheats
,
H.
Antoniadis
,
M.
Hueschen
,
W.
Leonard
,
J.
Miller
,
R.
Moon
,
D.
Roitman
, and
A.
Stocking
,
Science
273
,
884
(
1996
).
27.
J. E.
Bowen Katari
,
V. L.
Colvin
, and
A. P.
Alivisatos
,
J. Phys. Chem.
98
,
4109
(
1994
).
28.
D.
Schooss
,
A.
Mews
,
A.
Eychmuller
, and
H.
Weller
,
Phys. Rev. B
49
,
17
072
(
1994
).
This content is only available via PDF.
You do not currently have access to this content.