This letter examines the application of transparent MoOx (x < 3) films deposited by thermal evaporation directly onto crystalline silicon (c-Si) to create hole-conducting contacts for silicon solar cells. The carrier-selectivity of MoOx based contacts on both n- and p-type surfaces is evaluated via simultaneous consideration of the contact recombination parameter J0c and the contact resistivity ρc. Contacts made to p-type wafers and p+ diffused regions achieve optimum ρc values of 1 and 0.2 mΩ·cm2, respectively, and both result in a J0c of ∼200 fA/cm2. These values suggest that significant gains can be made over conventional hole contacts to p-type material. Similar MoOx contacts made to n-type silicon result in higher J0c and ρc with optimum values of ∼300 fA/cm2 and 30 mΩ·cm2 but still offer significant advantages over conventional approaches in terms of contact passivation, optical properties, and device fabrication.

1.
U.
Würfel
,
A.
Cuevas
, and
P.
Würfel
, “
Charge carrier separation in solar cells
,”
IEEE J. Photovoltaics
PP
(
99
),
9
(
2014
).
2.
D.
Yan
and
A.
Cuevas
, “
Empirical determination of the energy band gap narrowing in highly doped n+ silicon
,”
J. Appl. Phys.
114
(
4
),
044508
(
2013
).
3.
D.
Yan
and
A.
Cuevas
, “
Empirical determination of the energy band gap narrowing in p+ silicon heavily doped with boron
,”
J. Appl. Phys.
116
,
194505
(
2014
).
4.
P.
Altermatt
,
S.
Steingrube
,
Y.
Yang
,
C.
Sprodowski
,
T.
Dezhdar
,
S.
Koc
,
B.
Veith
,
S.
Herrman
,
R.
Bock
,
K.
Bothe
,
J.
Schmidt
, and
R.
Brendel
, “
Highly predictive modelling of entire Si solar cells for industrial applications
,” in
Proceedings of the 24th European Photovoltaic Solar Energy Conference
(
2009
).
5.
M.
Taguchi
,
A.
Yano
,
S.
Tohoda
,
K.
Matsuyama
,
Y.
Nakamura
,
T.
Nishiwaki
,
K.
Fujita
, and
E.
Maruyama
, “
24.7% record efficiency HIT solar cell on thin silicon wafer
,”
IEEE J. Photovoltaics
4
(
1
),
96
99
2014
.
6.
K.
Masuko
,
M.
Shigematsu
,
T.
Hashiguchi
,
D.
Fujishima
,
M.
Kai
,
N.
Yoshimura
,
T.
Yamaguchi
,
Y.
Ichihashi
,
T.
Mishima
,
N.
Matsubara
,
T.
Yamanishi
,
T.
Takahama
,
M.
Taguchi
,
E.
Maruyama
, and
S.
Okamoto
, “
Achievement of more than 25%; conversion efficiency with crystalline silicon heterojunction solar cell
,”
IEEE J. Photovoltaics
4
(
6
),
1433
1435
(
2014
).
7.
D.
Zielke
,
A.
Pazidis
,
F.
Werner
, and
J.
Schmidt
, “
Organic-silicon heterojunction solar cells on n-type silicon wafers: The BackPEDOT concept
,”
Sol. Energy Mater. Sol. Cells
131
,
110
116
(
2014
).
8.
J.
Schmidt
,
V.
Titova
, and
D.
Zielke
, “
Organic-silicon heterojunction solar cells: Open-circuit voltage potential and stability
,”
Appl. Phys. Lett.
103
(
18
),
183901
(
2013
).
9.
C.
Battaglia
,
X.
Yin
,
M.
Zheng
,
I. D.
Sharp
,
T.
Chen
,
S.
McDonnell
,
A.
Azcatl
,
C.
Carraro
,
B.
Ma
,
R.
Maboudian
,
R. M.
Wallace
, and
A.
Javey
, “
Hole selective MoOx contact for silicon solar cells
,”
Nano Lett.
14
(
2
),
967
971
(
2014
).
10.
C.
Battaglia
,
S. M. de
Nicolas
,
S. De
Wolf
,
X.
Yin
,
M.
Zheng
,
C.
Ballif
, and
A.
Javey
, “
Silicon heterojunction solar cell with passivated hole selective MoOx contact
,”
Appl. Phys. Lett.
104
(
11
),
113902
(
2014
).
11.
S.
Avasthi
,
W. E.
McClain
,
G.
Man
,
A.
Kahn
,
J.
Schwartz
, and
J. C.
Sturm
, “
Hole-blocking titanium-oxide/silicon heterojunction and its application to photovoltaics
,”
Appl. Phys. Lett.
102
(
20
),
203901
(
2013
).
12.
J.
Jhaveri
,
S.
Avasthi
,
K.
Nagamatsu
, and
J.
Sturm
, “
Stable low-recombination n-Si/TiO2 hole-blocking interface and its effect on silicon heterojunction photovoltaics
,” in
IEEE 40th Photovoltaic Specialist Conference (PVSC)
(
2014
).
13.
G. G.
Untila
,
T. N.
Kost
,
A. B.
Chebotareva
,
M. B.
Zaks
,
A. M.
Sitnikov
,
O. I.
Solodukha
, and
M. Z.
Shvarts
, “
Bifacial low concentrator argentum free crystalline silicon solar cells based on ARC of TCO and current collecting grid of copper wire
,”
AIP Conf. Proc.
1556
(
1
),
106
(
2013
).
14.
G.
Untila
,
T.
Kost
,
A.
Chebotareva
, and
M.
Timofeyev
, “
Optimization of the deposition and annealing conditions of fluorine-doped indium oxide films for silicon solar cells
,”
Semiconductors
47
(
3
),
415
421
(
2013
).
15.
J.
Meyer
,
S.
Hamwi
,
M.
Kroger
,
W.
Kowalsky
,
T.
Riedl
, and
A.
Kahn
, “
Transition metal oxides for organic electronics: Energetics, device physics and applications
,”
Adv. Mater.
24
(
40
),
5408
5427
(
2012
).
16.
S.
McDonnell
,
A.
Azcatl
,
R.
Addou
,
C.
Gong
,
C.
Battaglia
,
S.
Chuang
,
K.
Cho
,
A.
Javey
, and
R. M.
Wallace
, “
Hole contacts on transition metal dichalcogenides: Interface chemistry and band alignments
,”
ACS Nano
8
(
6
),
6265
6272
(
2014
).
17.
S.
Chuang
,
C.
Battaglia
,
A.
Azcatl
,
S.
McDonnell
,
J. S.
Kang
,
X.
Yin
,
M.
Tosun
,
R.
Kapadia
,
H.
Fang
,
R. M.
Wallace
, and
A.
Javey
, “
MoS2 p-type transistors and diodes enabled by high work function MoOx contacts
,”
Nano Lett.
14
(
3
),
1337
1342
(
2014
).
18.
M. T.
Greiner
,
L.
Chai
,
M. G.
Helander
,
W.-M.
Tang
, and
Z.-H.
Lu
, “
Transition metal oxide work functions: The influence of cation oxidation state and oxygen vacancies
,”
Adv. Funct. Mater.
22
(
21
),
4557
4568
(
2012
).
19.
R.
Swanson
and
D.
Kane
, “
Measurement of the emitter saturation current by a contactless photoconductivity decay method
,” in
Proceedings of 18th IEEE Photovoltaic Specialists Conference
(1985).
20.
K. R.
McIntosh
and
L. E.
Black
, “
On effective surface recombination parameters
,”
J. Appl. Phys.
116
(
1
),
014503
(
2014
).
21.
S. S.
Cohen
, “
Contact resistance and methods for its determination
,”
Thin Solid Films
104
(
3
),
361
379
(
1983
).
22.
M.
Grauvogl
and
R.
Hezel
, “
The truncated-pyramid MIS inversion-layer solar cell: A comprehensive analysis
,”
Prog. Photovoltaics
6
(
1
),
15
24
(
1998
).
23.
F.
Werner
,
Y.
Larionova
,
D.
Zielke
,
T.
Ohrdes
, and
J.
Schmidt
, “
Aluminum-oxide-based inversion layer solar cells on n-type crystalline silicon: Fundamental properties and efficiency potential
,”
J. Appl. Phys.
115
(
7
),
073702
(
2014
).
24.
R.
Cox
and
H.
Strack
, “
Ohmic contacts for GaAs devices
,”
Solid-State Electron.
10
(
12
),
1213
1218
(
1967
).
25.
M.
Tucci
,
L.
Serenelli
,
S. De
Iuliis
,
M.
Izzi
,
G. de
Cesare
, and
D.
Caputo
,
Contact Formation on a-Si:H/c-Si Heterostructure Solar Cells in Physics and Technology of Amorphous-Crystalline Heterostructure Silicon Solar Cells
, edited by
W. G. J. H. M.
van Sark
,
L.
Korte
, and
F.
Roca
(
Springer
,
2011
), pp.
331
376
.
26.
S.
Sze
and
K.
Ng
,
Physics of Semiconductor Devices
(
John Wiley & Sons
,
2006
).
27.
P.
Lolgen
,
W.
Sinke
,
C.
Leguijt
,
A.
Weeber
,
P.
Alkemade
, and
L.
Verhoef
, “
Boron doping of silicon using coalloying with aluminium
,”
Appl. Phys. Lett.
65
(
22
),
2792
2794
(
1994
).
28.
J.
Muller
,
K.
Bothe
,
S.
Gatz
,
H.
Plagwitz
,
G.
Schubert
, and
R.
Brendel
, “
Contact formation and recombination at screen-printed local aluminum-alloyed silicon solar cell base contacts
,”
IEEE Trans. Electron Devices
58
(
10
),
3239
3245
(
2011
).
29.
R.
Woehl
,
P.
Gundel
,
J.
Krause
,
K.
Ruhle
,
F.
Heinz
,
M.
Rauer
,
C.
Schmiga
,
M.
Schubert
,
W.
Warta
, and
D.
Biro
, “
Evaluating the aluminum-alloyed p+-layer of silicon solar cells by emitter saturation current density and optical microspectroscopy measurements
,”
IEEE Trans. Electron Devices
58
(
2
),
441
447
(
2011
).
30.
A.
Rohatgi
,
S.
Narasimha
, and
D. S.
Ruby
, “
Effective passivation of the low resistivity silicon surface by a rapid thermal oxide/PECVD silicon nitride stack and its application to passivated rear and bifacial Si solar cells
,” in
Proceedings of the 2nd World Conference on Photovoltaic Solar Energy Conversion
(
1998
).
31.
E.
Urrejola
,
K.
Peter
,
H.
Plagwitz
, and
G.
Schubert
, “
Al-Si alloy formation in narrow p-type Si contact areas for rear passivated solar cells
,”
J. Appl. Phys.
107
(
12
),
124516
(
2010
).
32.
J.
Schmidt
and
K.
Bothe
, “
Structure and transformation of the metastable boron- and oxygen-related defect center in crystalline silicon
,”
Phys. Rev. B
69
,
024107
(
2004
).
33.
C.
Mader
,
J.
Muller
,
S.
Eidelloth
, and
R.
Brendel
, “
Local rear contacts to silicon solar cells by in-line high-rate evaporation of aluminum
,”
Sol. Energy Mater. Sol. Cells
107
,
272
282
(
2012
).
34.
R.
Sinton
and
A.
Cuevas
, “
A quasi-steady-state open-circuit voltage method for solar cell characterization
,” in
16th European Photovoltaic Solar Energy Conference
(
2000
), Vol.
25
.
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