Laminated Carbon Nanotube Networks for Metal Electrode-Free ...
Supporting Information
Laminated Carbon Nanotube Networks for Metal Electrode-Free Efficient Perovskite Solar Cells Zhen Li†, Sneha A. Kulkarni †, Pablo P. Boix†, Enzheng Shi§, Anyuan Cao§, Kunwu Fu†,‡, Sudip K. Batabyal†, Jun Zhang┴, Qihua Xiong┴, Lydia Helena Wong†,‡,*, Nripan Mathews†,‡,ǁ,* and Subodh G. Mhaisalkar†,‡ † Energy Research Institute @ NTU (ERI@N), Nanyang Technological University, Techno Plaza, 50 Nanyang Drive, 637553, Singapore ‡ School of Materials Science and Engineering, Nanyang Technological University (NTU), Block N4.1, Nanyang Avenue, 639798, Singapore ǁ Singapore-Berkeley Research Initiative for Sustainable Energy, 1 Create Way, 138602, Singapore § Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, People’s Republic of China ┴ Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore
1
a
b
200 nm
5 nm
Figure S1. (a) TEM image of direct synthesized CNT film. (b) HRTEM image of a CNT bundle in the direct synthesized CNT film.
2
4
Raman intensity (a.u.)
7x10
4
6x10
G
4
5x10
4
4x10
4
3x10
4
2x10
4 1x10 RBM D 0 0 500 1000 1500 -1 Wavenumber (cm )
2000
Figure S2. Raman spectrum of CVD synthesized carbon nanotube film under the excitation of 633 nm laser. The G band at 1587 cm-1 is derived from the sp2 carbon and is a signature of the graphitic structure of CNTs. The D band at 1322 cm-1 is derived from the sp3 carbon features and is a signature of the defects and disorder in the CNTs graphitic walls as well as the amorphous carbon impurity on the CNT surface. The G/D ratio of 37 indicates low content of amorphous carbon impurities in the film. The RBM (radial breathing mode) peaks are the Raman signatures of single-walled or few-walled CNTs.
3
Figure
S3.
Cross
section
SEM
image
of
(a)
CH3NH3PbI3/CNT
and
(b)
CH3NH3PbI3/CNT/spiro-OMeTAD solar cells. Inset of figure a is cross section SEM image of perovskite substrate before CNT coating. The CH3NH3PbI3 perovskite with mesoporous TiO2 is about 700 nm. The thickness of CNT film coated on the provskite layer was about 20-30 nm. The ultrathin CNT film was flexible that it could welladjusted to the nanometer scale roughness of the CH3NH3PbI3 layer. After spin coating of spiro-OMeTAD, the HTM infiltrated into CNTs networks and forms a spiroOMeTAD/CNTs composite layer. Carbon nanotube bundles were pulled out from solar cells and stretched down over the CH3HN3PbI3/TiO2 layer when the samples were crosssectioned for imaging. The CNTs remained on top of the perovskite layer in actual devices.
4
Transmittance (%)
60
40
S4.
CH3NH3PbI3/CNTs
20
0
Figure
CH3NH3PbI3/CNTs
/spiro-OMeTAD
400
UV-Vis-IR
600 800 1000 1200 1400 Wavelength (nm) transmittance
spectra
of
CH3NH3PbI3/CNTs
and
CH3NH3PbI3/CNTs/spiro-OMeTAD solar cells.
5
a
b CNTs
Figure S5. SEM images of CNT film after spiro-OMeTAD spin coating. (a) Low magnification image showing that spiro-OMeTAD fully covered the CNT surface. (b) High magnification image of a small region with CNTs exposed from the spiroOMeTAD coating.
6
(a)
(b)
Figure S6. (a) Capacitance Bode plot of solar cells with and without spiro-OMeTAD measured at 800 mV applied bias under 0.1 sun; fittings represented by solid lines are following the equivalent circuit shown in the inset. (b) Band diagram for TiO2, CH3NH3PbI3, spiro-OMeTAD and CNTs.
7
(b)
-3.0
2
Current density (mA/cm )
(a) CNT + spiro-OMeTAD CNT
-2.5
CNT CNT+spiro-OMeTAD
-2.0 -1.5 -1.0 -0.5 0.0 0.0
0.2
0.4 0.6 0.8 Voltage (V)
1.0
Figure S7. (a) Total series resistance (series resistance, Rs, plus hole transporting resistance, RHTM) extracted from the impedance spectroscopy fittings. (b) Dark current curves of solar cells with and without spiro-OMeTAD.
8
FTO side CNT+spiro-OMeTAD side
2
Current density (mA/cm )
25 20 15 10 5 0 0.0
0.2
0.4
0.6
0.8
1.0
Voltage (V)
Figure S8. J-V curves of CH3NH3PbI3/CNT/spiro-OMeTAD solar cell illuminated from FTO or CNT+spiro-OMeTAD side
9
Table S1. Performance parameters of solar cells with CNT electrode
Samples
VOC（mV） ）
JSC（mA/cm2）
FF (%)
PCE（ （%） ）
1
856
16.72
43.9
6.29
2
838
13.99
51.6
6.05
3
881
15.47
50.4
6.87
4
869
16.44
44.1
6.31
5
858
13.90
43.1
5.14
6
868
10.05
51.5
4.49
Table S2. Performance parameters of solar cells with CNTs and CNTs/spiro-OMeTAD composite electrode
JSC（mA/cm2）
Samples
VOC（mV） ）
5 (CNTs)
858
13.90
43.1
5.14
5+spiro-OMeTAD
999
18.11
54.7
9.90
6 (CNTs)
868
10.05
51.5
4.49
6+spiro-OMeTAD
976
13.38
62.2
8.13
FF (%)
PCE（ （%） ）
10
Laminated Carbon Nanotube Networks for Metal Electrode-Free Efficient Perovskite Solar Cells Zhen Li†, Sneha A. Kulkarni †, Pablo P. Boix†, Enzheng Shi§, Anyuan Cao§, Kunwu Fu†,‡, Sudip K. Batabyal†, Jun Zhang┴, Qihua Xiong┴, Lydia Helena Wong†,‡,*, Nripan Mathews†,‡,ǁ,* and Subodh G. Mhaisalkar†,‡ † Energy Research Institute @ NTU (ERI@N), Nanyang Technological University, Techno Plaza, 50 Nanyang Drive, 637553, Singapore ‡ School of Materials Science and Engineering, Nanyang Technological University (NTU), Block N4.1, Nanyang Avenue, 639798, Singapore ǁ Singapore-Berkeley Research Initiative for Sustainable Energy, 1 Create Way, 138602, Singapore § Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, People’s Republic of China ┴ Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore
1
a
b
200 nm
5 nm
Figure S1. (a) TEM image of direct synthesized CNT film. (b) HRTEM image of a CNT bundle in the direct synthesized CNT film.
2
4
Raman intensity (a.u.)
7x10
4
6x10
G
4
5x10
4
4x10
4
3x10
4
2x10
4 1x10 RBM D 0 0 500 1000 1500 -1 Wavenumber (cm )
2000
Figure S2. Raman spectrum of CVD synthesized carbon nanotube film under the excitation of 633 nm laser. The G band at 1587 cm-1 is derived from the sp2 carbon and is a signature of the graphitic structure of CNTs. The D band at 1322 cm-1 is derived from the sp3 carbon features and is a signature of the defects and disorder in the CNTs graphitic walls as well as the amorphous carbon impurity on the CNT surface. The G/D ratio of 37 indicates low content of amorphous carbon impurities in the film. The RBM (radial breathing mode) peaks are the Raman signatures of single-walled or few-walled CNTs.
3
Figure
S3.
Cross
section
SEM
image
of
(a)
CH3NH3PbI3/CNT
and
(b)
CH3NH3PbI3/CNT/spiro-OMeTAD solar cells. Inset of figure a is cross section SEM image of perovskite substrate before CNT coating. The CH3NH3PbI3 perovskite with mesoporous TiO2 is about 700 nm. The thickness of CNT film coated on the provskite layer was about 20-30 nm. The ultrathin CNT film was flexible that it could welladjusted to the nanometer scale roughness of the CH3NH3PbI3 layer. After spin coating of spiro-OMeTAD, the HTM infiltrated into CNTs networks and forms a spiroOMeTAD/CNTs composite layer. Carbon nanotube bundles were pulled out from solar cells and stretched down over the CH3HN3PbI3/TiO2 layer when the samples were crosssectioned for imaging. The CNTs remained on top of the perovskite layer in actual devices.
4
Transmittance (%)
60
40
S4.
CH3NH3PbI3/CNTs
20
0
Figure
CH3NH3PbI3/CNTs
/spiro-OMeTAD
400
UV-Vis-IR
600 800 1000 1200 1400 Wavelength (nm) transmittance
spectra
of
CH3NH3PbI3/CNTs
and
CH3NH3PbI3/CNTs/spiro-OMeTAD solar cells.
5
a
b CNTs
Figure S5. SEM images of CNT film after spiro-OMeTAD spin coating. (a) Low magnification image showing that spiro-OMeTAD fully covered the CNT surface. (b) High magnification image of a small region with CNTs exposed from the spiroOMeTAD coating.
6
(a)
(b)
Figure S6. (a) Capacitance Bode plot of solar cells with and without spiro-OMeTAD measured at 800 mV applied bias under 0.1 sun; fittings represented by solid lines are following the equivalent circuit shown in the inset. (b) Band diagram for TiO2, CH3NH3PbI3, spiro-OMeTAD and CNTs.
7
(b)
-3.0
2
Current density (mA/cm )
(a) CNT + spiro-OMeTAD CNT
-2.5
CNT CNT+spiro-OMeTAD
-2.0 -1.5 -1.0 -0.5 0.0 0.0
0.2
0.4 0.6 0.8 Voltage (V)
1.0
Figure S7. (a) Total series resistance (series resistance, Rs, plus hole transporting resistance, RHTM) extracted from the impedance spectroscopy fittings. (b) Dark current curves of solar cells with and without spiro-OMeTAD.
8
FTO side CNT+spiro-OMeTAD side
2
Current density (mA/cm )
25 20 15 10 5 0 0.0
0.2
0.4
0.6
0.8
1.0
Voltage (V)
Figure S8. J-V curves of CH3NH3PbI3/CNT/spiro-OMeTAD solar cell illuminated from FTO or CNT+spiro-OMeTAD side
9
Table S1. Performance parameters of solar cells with CNT electrode
Samples
VOC（mV） ）
JSC（mA/cm2）
FF (%)
PCE（ （%） ）
1
856
16.72
43.9
6.29
2
838
13.99
51.6
6.05
3
881
15.47
50.4
6.87
4
869
16.44
44.1
6.31
5
858
13.90
43.1
5.14
6
868
10.05
51.5
4.49
Table S2. Performance parameters of solar cells with CNTs and CNTs/spiro-OMeTAD composite electrode
JSC（mA/cm2）
Samples
VOC（mV） ）
5 (CNTs)
858
13.90
43.1
5.14
5+spiro-OMeTAD
999
18.11
54.7
9.90
6 (CNTs)
868
10.05
51.5
4.49
6+spiro-OMeTAD
976
13.38
62.2
8.13
FF (%)
PCE（ （%） ）
10
