240
M. Hiramoto
Fig. 9.11 a Fermi level (E F ) vs. molar doping ratio (MR). Pentacene (P5) films are doped with
an acceptor (C 60 F 36 ) (downward triangles) or donor (W 2 (hpp) 4 ) (upright triangles). b Statistical
description of acceptor doping. Activation of the dopant occurs at an effective acceptor level E A .
Trap levels E T prevent doping at low concentrations. Free holes appear under the doping condition,
N A > N T . c Dependences of the work function (black dots) and HOMO peak position (stars) on E F
by doping. The top- and bottom-dashed horizontal lines represent the work function and HOMO
of the intrinsic C 60 film, respectively. d Dependences of the mobility of a C 60 layer on the doping
concentration. (a) Reproduced with permission from [10]. Copyright 2015 John Wiley and Sons.
(b) Reproduced with permission from [10]. Copyright 2015 John Wiley and Sons. Reproduced
with permission from [51]. Copyright 2012 American Physical Society. (c) (d) Reproduced with
permission from [23]. Copyright 2012 American Physical Society
Trap Filling by Acceptor Doping
Trap filling was discovered by Tietze et al. through acceptor doping for hole transporting organic films [51] and for pentacene films [10]. Pentacene films were doped
with C 60 F 36 acting as an acceptor. At doping concentrations below 4 × 10
−5 , the
E F measured by ultraviolet photoelectron spectroscopy (UPS) was pinned near its
intrinsic condition (E F ≈ 1.8 eV) (Fig. 9.11a). A slight increase in the doping ratio
M. Hiramoto
Fig. 9.11 a Fermi level (E F ) vs. molar doping ratio (MR). Pentacene (P5) films are doped with
an acceptor (C 60 F 36 ) (downward triangles) or donor (W 2 (hpp) 4 ) (upright triangles). b Statistical
description of acceptor doping. Activation of the dopant occurs at an effective acceptor level E A .
Trap levels E T prevent doping at low concentrations. Free holes appear under the doping condition,
N A > N T . c Dependences of the work function (black dots) and HOMO peak position (stars) on E F
by doping. The top- and bottom-dashed horizontal lines represent the work function and HOMO
of the intrinsic C 60 film, respectively. d Dependences of the mobility of a C 60 layer on the doping
concentration. (a) Reproduced with permission from [10]. Copyright 2015 John Wiley and Sons.
(b) Reproduced with permission from [10]. Copyright 2015 John Wiley and Sons. Reproduced
with permission from [51]. Copyright 2012 American Physical Society. (c) (d) Reproduced with
permission from [23]. Copyright 2012 American Physical Society
Trap Filling by Acceptor Doping
Trap filling was discovered by Tietze et al. through acceptor doping for hole transporting organic films [51] and for pentacene films [10]. Pentacene films were doped
with C 60 F 36 acting as an acceptor. At doping concentrations below 4 × 10
−5 , the
E F measured by ultraviolet photoelectron spectroscopy (UPS) was pinned near its
intrinsic condition (E F ≈ 1.8 eV) (Fig. 9.11a). A slight increase in the doping ratio