Carrier dynamics of an organic molecular semiconductor, rubrene, was investigated by optical-pump terahertz-probe spectroscopy from 1 to 15 THz. At 294 K, a Drude-like response due to photogenerated hole carriers is observed below 8 THz. The real part σ1(ω) of the optical conductivity is suppressed below 2 THz, indicating the presence of a localization effect. Such a spectral feature was reproduced by a Drude-Anderson model including the effect of dynamical disorder due to intermolecular vibrations. At 50 K, the spectral weight of σ1(ω) due to photocarriers shifts to lower frequency below 4 THz and the suppression of σ1(ω) is hardly observed, which we associate with a reduction of thermal molecular motions. The overall photocarrier generation and recombination dynamics is also discussed.

1.
V.
Podzorov
,
E.
Menard
,
A.
Borissov
,
V.
Kiryukhin
,
J. A.
Rogers
, and
M. E.
Gershenson
,
Phys. Rev. Lett.
93
,
086602
(
2004
).
2.
J.
Takeya
,
M.
Yamagishi
,
Y.
Tominari
,
R.
Hirahara
,
Y.
Nakazawa
,
T.
Nishikawa
,
T.
Kawase
,
T.
Shimoda
, and
S.
Ogawa
,
Appl. Phys. Lett.
90
,
102120
(
2007
).
3.
V.
Podzorov
,
E.
Menard
,
J. A.
Rogers
, and
M. E.
Gershenson
,
Phys. Rev. Lett.
95
,
226601
(
2005
).
4.
J.
Takeya
,
J.
Kato
,
K.
Hara
,
M.
Yamagishi
,
R.
Hirahara
,
K.
Yamada
,
Y.
Nakazawa
,
S.
Ikehata
,
K.
Tsukagoshi
,
Y.
Aoyagi
,
T.
Takenobu
, and
Y.
Iwasa
,
Phys. Rev. Lett.
98
,
196804
(
2007
).
5.
Y.
Nakayama
,
Y.
Uragami
,
S.
Machida
,
K. R.
Koswattage
,
D.
Yoshimura
,
H.
Setoyama
,
T.
Okajima
,
K.
Mase
, and
H.
Ishii
,
Appl. Phys. Express
5
,
111601
(
2012
).
6.
S.
Machida
,
Y.
Nakayama
,
S.
Duhm
,
Q.
Xin
,
A.
Funakoshi
,
N.
Ogawa
,
S.
Kera
,
N.
Ueno
, and
H.
Ishii
,
Phys. Rev. Lett.
104
,
156401
(
2010
).
7.
A.
Troisi
and
G.
Orlandi
,
Phys. Rev. Lett.
96
,
086601
(
2006
).
8.
S.
Ciuchi
,
S.
Fratini
, and
D.
Mayou
,
Phys. Rev. B
83
,
081202(R)
(
2011
).
9.
V.
Cataudella
,
G. De
Filippis
, and
C. A.
Perroni
,
Phys. Rev. B
83
,
165203
(
2011
).
10.
S.
Ciuchi
and
S.
Fratini
,
Phys. Rev. B
86
,
245201
(
2012
).
11.
S.
Fratini
,
S.
Ciuchi
, and
D.
Mayou
,
Phys. Rev. B
89
,
235201
(
2014
).
12.
M.
Fischer
,
M.
Dressel
,
B.
Gompf
,
A. K.
Tripathi
, and
J.
Pflaum
,
Appl. Phys. Lett.
89
,
182103
(
2006
).
13.
Z. Q.
Li
,
V.
Podzorov
,
N.
Sai
,
M. C.
Martin
,
M. E.
Gershenson
,
M. D.
Ventra
, and
D. N.
Basov
,
Phys. Rev. Lett.
99
,
016403
(
2007
).
14.
R.
Uchida
,
H.
Yada
,
M.
Makino
,
Y.
Matsui
,
K.
Miwa
,
T.
Uemura
,
J.
Takeya
, and
H.
Okamoto
,
Appl. Phys. Lett.
102
,
093301
(
2013
).
15.
N. A.
Minder
,
S.
Lu
,
S.
Fratini
,
S.
Ciuchi
,
A.
Facchetti
, and
A. F.
Morpurgo
,
Adv. Mater.
26
,
1254
(
2014
).
16.
S.
Tao
,
H.
Matsuzaki
,
H.
Uemura
,
H.
Yada
,
T.
Uemura
,
J.
Takeya
,
T.
Hasegawa
, and
H.
Okamoto
,
Phys. Rev. B
83
,
075204
(
2011
).
17.
S.
Tao
,
N.
Ohtani
,
R.
Uchida
,
T.
Miyamoto
,
Y.
Matsui
,
H.
Yada
,
H.
Uemura
,
H.
Matsuzaki
,
T.
Uemura
,
J.
Takeya
, and
H.
Okamoto
,
Phys. Rev. Lett.
109
,
097403
(
2012
).
18.
F. A.
Hegmann
,
R. R.
Tykwinski
,
K. P. H.
Lui
,
J. E.
Bullock
, and
J. E.
Anthony
,
Phys. Rev. Lett.
89
,
227403
(
2002
).
19.
V. K.
Thorsmølle
,
R. D.
Averitt
,
X.
Chi
,
D. J.
Hilton
,
D. L.
Smith
,
A. P.
Ramirez
, and
A. J.
Taylor
,
Appl. Phys. Lett.
84
,
891
(
2004
).
20.
O.
Ostroverkhova
,
D. G.
Cooke
,
S.
Shcherbyna
,
R. F.
Egerton
,
F. A.
Hegmann
,
R. R.
Tykwinski
, and
J. E.
Anthony
,
Phys. Rev. B
71
,
035204
(
2005
).
21.
H. A. V.
Laarhoven
,
C. F. J.
Flipse
,
M.
Koeberg
,
M.
Bonn
,
E.
Hendry
,
G.
Orlandi
,
O. D.
Jurchescu
,
T. T. M.
Palstra
, and
A.
Troishi
,
J. Chem. Phys.
129
,
044704
(
2008
).
22.
O.
Ostroverkhova
,
D. G.
Cooke
,
F. A.
Hegmann
,
J. E.
Anthony
,
V.
Podzorov
,
M. E.
Gershenson
,
O. D.
Jurchescu
, and
T. T. M.
Palstra
,
Appl. Phys. Lett.
88
,
162101
(
2006
).
23.
M.
Koeberg
,
E.
Hendry
,
J. M.
Schins
,
H. A. v.
Laarhoven
,
C. F. J.
Flipse
,
K.
Reimann
,
M.
Woerner
,
T.
Elsaesser
, and
M.
Bonn
,
Phys. Rev. B
75
,
195216
(
2007
).
24.
D. J.
Cook
and
R. M.
Hochstrasser
,
Opt. Lett.
25
,
1210
(
2000
).
25.
K. Y.
Kim
,
J. H.
Glownia
,
A. J.
Taylor
, and
G.
Rodriguez
,
Opt. Express
15
,
4577
(
2007
).
26.
J.
Dai
,
N.
Karpowicz
, and
X.-C.
Zhang
,
Phys. Rev. Lett.
103
,
023001
(
2009
).
27.
E.
Matsubara
,
M.
Nagai
, and
M.
Ashida
,
Appl. Phys. Lett.
101
,
011105
(
2012
).
28.
See supplementary material at http://dx.doi.org/10.1063/1.4897530 about the details of optical-pump terahertz-probe spectroscopy and the analyses of time evolutions of ΔOD.
29.
P.
Irkhin
,
A.
Ryasnyanskiy
,
M.
Koehler
, and
I.
Biaggio
,
Phys Rev. B
86
,
085143
(
2012
).
30.

The excitation photon density xph was defined by the photon density per unit volume within the absorption depth and evaluated by xph = (1 – 1/e)(1 – Rp)Ip/lp, where Ip, lp, Rp, and e are the excitation photon density per unit area, the absorption depth, the reflection loss of the pump light, and Napeier's constant, respectively.

31.
O.
Mitrofanov
,
D. V.
Lang
,
C.
Kloc
,
J. M.
Wikberg
,
T.
Siegrist
,
W.-Y.
So
,
M. A.
Sergent
, and
A. P.
Ramirez
,
Phys. Rev. Lett.
97
,
166601
(
2006
).
32.

At around td = 0.2 ps, ΔOD sharply decreases as shown in Fig. 2(b), indicating that photoexcited states largely change within the duration of a probe pulse. To minimize non-equilibrium effects arising at the initial stage after the photoexcitation, we analyzed σ̃(ω) at 5 ps.

33.

In this analysis, we cannot determine N and L values, since the hole generation efficiency is unknown.

34.
J. R.
Weinberg-Wolf
,
L. E.
McNeil
,
S.
Liu
, and
C.
Kloc
,
J. Phys.: Condens. Matter
19
,
276204
(
2007
).
35.
E.
Venuti
,
I.
Bilotti
,
R. G. D.
Valle
,
A.
Brillante
,
P.
Ranzieri
,
M.
Masino
, and
A.
Girlando
,
J. Phys. Chem. C
112
,
17416
(
2008
).
36.
G.
Nan
,
X.
Yang
,
L.
Wang
,
Z.
Shuai
, and
Y.
Zhao
,
Phys. Rev. B
79
,
115203
(
2009
).
37.
A.
Girlando
,
L.
Grisanti
,
M.
Masino
,
I.
Bilotti
,
A.
Brillante
,
R. G. D.
Valle
, and
E.
Venuti
,
Phys. Rev. B
82
,
035208
(
2010
).
38.
H.
Najafov
,
I.
Biaggio
,
V.
Podzorov
,
M. F.
Calhoun
, and
M. E.
Gershenson
,
Phys. Rev. Lett.
96
,
056604
(
2006
).

Supplementary Material

You do not currently have access to this content.