Perovskite Solar Cell Using Two-Dimensional Titania Nanosheet Thin ...
Supporting Information
Perovskite Solar Cell Using Two-Dimensional Titania Nanosheet Thin Film as Compact Layer Can Li,† Yahui Li,† Yujin Xing,‡ Zelin Zhang,† Xianfeng Zhang,§ Zhen Li,┴ Yantao Shi,‡ Tingli Ma,‡ Renzhi Ma,|| Kunlin Wang,† Jinquan Wei*,† †
Key Lab for Advance Materials Processing Technology of Education Ministry, State
Key Lab of New Ceramic and Fine Processing, and School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China ‡
State Key Laboratory of Fine Chemicals, School of Chemistry, Dalian University of
Technology, Dalian, 116024, P. R. China §
National Center for Nanoscience and Technology, Beiyitiao 11, Beijing 100190, P. R.
China ┴
National Renewable Energy Laboratory, Golden, Colorado 80401, United States
||
National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 3050044, Japan
Corresponding Author: Jinquan Wei. Email: [email protected]. Tel: +86-10-62781065.
S1
Methods Materials. TNS/TBA+ colloidal solution was prepared by chemical exfoliation method according to the recent report.
1, 2, 3
The concentration of the TNS in the TBA+ solution is 4
g/L. The reagents used for fabricating perovskite solar cells were purchased from three companies: PbI2, N, N-dimethylformamide (DMF), 4-tert-butylpyridine (tBP), and lithium bis(trifluoromethylsulphonyl)imide (TFSI) were from Sigma Aldrich, China; TiO2 paste, CH3NH3I
and
FK102
dopant
were
from
Dyesol,
Australia;
2,2’,7,7’-tetrakis(N,N-di-p-methoxyphenylamine)-9,9’-spirobifluorene (spiro-OMeTAD) was from Lumtec, Taiwan. All reagents were used as received.
Preparation of TNS thin film.
FTO glass (TEC7, Pilkington) was subsequently
cleaned with detergent, deionized water, acetone, 2-propanol, ethanol, deionized water, and dried by nitrogen gas. The EPD of TNS thin film was carried out by a 3-electrode method, where two clean FTO substrates were used as working (anode) and counter electrodes (cathode), and Ag/AgCl was used as reference electrode, respectively. The working and counter electrodes were placed parallel to each other with a distance of 8 mm. A potential between working and counter electrodes was applied by an electrochemical workstation (CHI660E). After the EPD process, a FTO substrate with TNS thin film was annealed at 500 °C for 1 hour. The thickness of the TNS film was measured by scanning electron microscopy under high magnification. We measured several positions and used the average value for the thickness of the TNS thin film.
S2
Preparation of titanium oxide compact layer by spin-coating. 32.5 μL of 2M HCl was added into 5 ml ethanol and then 350 μL titanium isopropoxide was added drop wise into the ethanol solution. The titanium oxide precursor was spin coated onto cleaned FTO substrate at 2000 rpm for 60 s and then annealed at 500 °C for 30 min.
Device fabrication. A mesoporous TiO2 layer was deposited on the FTO substrate with TNS or TNP compact layer by spin coating TiO2 paste (Dyesol-18NRT, Dyesol) diluted in ethanol (2:7, weight ratio) at 5000 rpm for 30 s and annealed at 500 °C for 30 min. The perovskite CH3NH3PbI3 layer was fabricated by a sequential deposition method according to recent report.4 In brief, 462 mg PbI2 was dissolved in 1 mL DMF solution under stirring condition at 70 °C. The mesoporous TiO2 layer was then filtrated with PbI2 solution by spin coating at 6500 rpm for 5 s followed by annealing at 70 °C for 30 min. Subsequently, the mesoporous TiO2 with PbI2 was dipped in a solution of CH3NH3I in 2-propanol (10 mg/mL) for 20 min, rinsed with 2-propanol and dried at 70 °C for 30 min. A hole transporting material (HTM) was spin coated on perovskite layer at 4000 rpm for 30 s. The HTM solution was prepared by dissolving 72.3 mg spiro-OMeTAD, 29 μL 4-tert-butylpyridine (tBP), 17.5 μL of a stock solution of 520 mg/mL TFSI in acetonitrile and 29 μL of a stock solution of 300 mg/mL FK102 dopant in acetonitrile in 1 mL chlorobenzene. Finally, a gold thin film (60 nm) was evaporated on top of the device to form a back electrode by an e-beam evaporator. The active area of this electrode was fixed at 0.08 cm2.
Characterization. Morphology and structure of the TNS thin films and perovskite solar cells were characterized by field-emission scanning electron microscopy (Nova nanoSEM S3
430, FEI), X-ray diffraction (Smartlab, Rigaku), atomic force microscopy (5100 SPM, Agilent), and UV-vis absorption spectra (UV2450, SHIMADZU). The thickness of TNS thin film was measured by filed-emission scanning electron microscopy (Nova nanoSEM 430, FEI). The dark and light current-voltage curves of the solar cells were measured under one solar illumination (AM 1.5G, 100 mW cm-2, 91195, Newport) connected with a semiconductor characterization system (4200-SCS, Keithley). The hysteresis effect of the PSCs were measured by forward and reverse scan with a scan rate of 100 mV/s.
S4
Supporting Figures
Figure S1: SEM image of a TNS thin film with deposition time of 60 s. As shown by dark arrows, there are lots of tiny holes in some TNS films prepared by short-time deposition.
Figure S2: High magnification SEM images of the TNS thin film with different deposition time. (a)2 min, (b)5 min, (c)10 min, (d) 15 min. The thicknesses of the TNS film were
S5
measured by using the distance measuring tools in SEM under high magnification. We used the average thickness in the manuscript.
Figure S3: The dependence of thickness of TNS thin films on the electrophoretic deposition time. The thickness of the TNS thin film is almost linear to EPD time.
Figure S4: SEM images of TNP (a) and TNS (b) thin film on the FTO surface. The TNP film has a thickness of about 50 nm, while the TNS has thickness only about 15 nm.
S6
Figure S5: Cross-sectional SEM image of a perovskite solar cell using TiO2 nanoparticle (TNP) thin film as compact layer, showing the structure and quality of the PSC. Due to some pinholes in the perovskite capping layer, hole-transport materials (spiro-OMeTAD) might permeate to the mesoporous layer.
Figure S6: Histogram of the PCE data for PSCs using TNS film prepared from 5 min EPD as the compact layer. The PSC has a mean efficiency of 9.3% and the highest value of 10.7%.
S7
Figure S7: Photovoltaic parameters of the CH3NH3PbI3 solar cells depend on the deposition time of TNS compact layers. Every deposition condition has at least 8 devices.
Figure S8: The difference of current between forward scan and reverse scan (ΔI=Iforward-Ireverse) for the TNS/FTO and TNP/FTO films.
S8
Table S1: Photovoltaic properties of the CH3NH3PbI3 perovskite solar cells using TNS and TNP as the compact layers in the hysteresis measurement. Voc (mV)
Jsc (mA cm-2)
FF
PCE (%)
TNS, Forward
888
17.3
0.60
9.2
TNS, Reverse
917
17.5
0.67
10.7
TNP, Forward
858
19.4
0.52
8.6
TNP, Reverse
855
21.5
0.58
10.7
References (1)
Li, L.; Ma, R. Z.; Ebina, Y.; Fukuda, K.; Takada, K.; Sasaki, T. Layer-by-Layer Assembly and Spontaneous Flocculation of Oppositely Charged Oxide and Hydroxide Nanosheets into Inorganic Sandwich Layered Materials J. Am. Chem. Soc. 2007, 129, 8000–8007.
(2)
Ohwada, M.; Kimoto, K; Mizoguchi, T.; Ebina, Y.; Sasaki, T. Atomic Structure of Titania Nanosheet with Vacancies. Sci. Rep. 2013, 3, 2801.
(3)
Sasaki,
T.;
Watanabe,
M.;
Hashizume,
H.;
Yamada,
H.;
Nakazawa,
H.
Macromolecule-like Aspects for a Colloidal Suspension of an Exfoliated Titanate. Pairwise Association of Nanosheets and Dynamic Reassembling Process Initiated from It. J. Am. Chem. Soc. 1996, 118, 8329–8335. (4)
Burschka, J.; Pellet, N.; Moon, S. J.; Baker, R. H.; Gao, P.; Nazeeruddin, M. K.; Grätzel,
M.
Sequential
Deposition
as
a
Route
Perovskite-Sensitized Solar Cells Nature 2013, 499, 316–319
S9
to
High-Performance
Perovskite Solar Cell Using Two-Dimensional Titania Nanosheet Thin Film as Compact Layer Can Li,† Yahui Li,† Yujin Xing,‡ Zelin Zhang,† Xianfeng Zhang,§ Zhen Li,┴ Yantao Shi,‡ Tingli Ma,‡ Renzhi Ma,|| Kunlin Wang,† Jinquan Wei*,† †
Key Lab for Advance Materials Processing Technology of Education Ministry, State
Key Lab of New Ceramic and Fine Processing, and School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China ‡
State Key Laboratory of Fine Chemicals, School of Chemistry, Dalian University of
Technology, Dalian, 116024, P. R. China §
National Center for Nanoscience and Technology, Beiyitiao 11, Beijing 100190, P. R.
China ┴
National Renewable Energy Laboratory, Golden, Colorado 80401, United States
||
National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 3050044, Japan
Corresponding Author: Jinquan Wei. Email: [email protected]. Tel: +86-10-62781065.
S1
Methods Materials. TNS/TBA+ colloidal solution was prepared by chemical exfoliation method according to the recent report.
1, 2, 3
The concentration of the TNS in the TBA+ solution is 4
g/L. The reagents used for fabricating perovskite solar cells were purchased from three companies: PbI2, N, N-dimethylformamide (DMF), 4-tert-butylpyridine (tBP), and lithium bis(trifluoromethylsulphonyl)imide (TFSI) were from Sigma Aldrich, China; TiO2 paste, CH3NH3I
and
FK102
dopant
were
from
Dyesol,
Australia;
2,2’,7,7’-tetrakis(N,N-di-p-methoxyphenylamine)-9,9’-spirobifluorene (spiro-OMeTAD) was from Lumtec, Taiwan. All reagents were used as received.
Preparation of TNS thin film.
FTO glass (TEC7, Pilkington) was subsequently
cleaned with detergent, deionized water, acetone, 2-propanol, ethanol, deionized water, and dried by nitrogen gas. The EPD of TNS thin film was carried out by a 3-electrode method, where two clean FTO substrates were used as working (anode) and counter electrodes (cathode), and Ag/AgCl was used as reference electrode, respectively. The working and counter electrodes were placed parallel to each other with a distance of 8 mm. A potential between working and counter electrodes was applied by an electrochemical workstation (CHI660E). After the EPD process, a FTO substrate with TNS thin film was annealed at 500 °C for 1 hour. The thickness of the TNS film was measured by scanning electron microscopy under high magnification. We measured several positions and used the average value for the thickness of the TNS thin film.
S2
Preparation of titanium oxide compact layer by spin-coating. 32.5 μL of 2M HCl was added into 5 ml ethanol and then 350 μL titanium isopropoxide was added drop wise into the ethanol solution. The titanium oxide precursor was spin coated onto cleaned FTO substrate at 2000 rpm for 60 s and then annealed at 500 °C for 30 min.
Device fabrication. A mesoporous TiO2 layer was deposited on the FTO substrate with TNS or TNP compact layer by spin coating TiO2 paste (Dyesol-18NRT, Dyesol) diluted in ethanol (2:7, weight ratio) at 5000 rpm for 30 s and annealed at 500 °C for 30 min. The perovskite CH3NH3PbI3 layer was fabricated by a sequential deposition method according to recent report.4 In brief, 462 mg PbI2 was dissolved in 1 mL DMF solution under stirring condition at 70 °C. The mesoporous TiO2 layer was then filtrated with PbI2 solution by spin coating at 6500 rpm for 5 s followed by annealing at 70 °C for 30 min. Subsequently, the mesoporous TiO2 with PbI2 was dipped in a solution of CH3NH3I in 2-propanol (10 mg/mL) for 20 min, rinsed with 2-propanol and dried at 70 °C for 30 min. A hole transporting material (HTM) was spin coated on perovskite layer at 4000 rpm for 30 s. The HTM solution was prepared by dissolving 72.3 mg spiro-OMeTAD, 29 μL 4-tert-butylpyridine (tBP), 17.5 μL of a stock solution of 520 mg/mL TFSI in acetonitrile and 29 μL of a stock solution of 300 mg/mL FK102 dopant in acetonitrile in 1 mL chlorobenzene. Finally, a gold thin film (60 nm) was evaporated on top of the device to form a back electrode by an e-beam evaporator. The active area of this electrode was fixed at 0.08 cm2.
Characterization. Morphology and structure of the TNS thin films and perovskite solar cells were characterized by field-emission scanning electron microscopy (Nova nanoSEM S3
430, FEI), X-ray diffraction (Smartlab, Rigaku), atomic force microscopy (5100 SPM, Agilent), and UV-vis absorption spectra (UV2450, SHIMADZU). The thickness of TNS thin film was measured by filed-emission scanning electron microscopy (Nova nanoSEM 430, FEI). The dark and light current-voltage curves of the solar cells were measured under one solar illumination (AM 1.5G, 100 mW cm-2, 91195, Newport) connected with a semiconductor characterization system (4200-SCS, Keithley). The hysteresis effect of the PSCs were measured by forward and reverse scan with a scan rate of 100 mV/s.
S4
Supporting Figures
Figure S1: SEM image of a TNS thin film with deposition time of 60 s. As shown by dark arrows, there are lots of tiny holes in some TNS films prepared by short-time deposition.
Figure S2: High magnification SEM images of the TNS thin film with different deposition time. (a)2 min, (b)5 min, (c)10 min, (d) 15 min. The thicknesses of the TNS film were
S5
measured by using the distance measuring tools in SEM under high magnification. We used the average thickness in the manuscript.
Figure S3: The dependence of thickness of TNS thin films on the electrophoretic deposition time. The thickness of the TNS thin film is almost linear to EPD time.
Figure S4: SEM images of TNP (a) and TNS (b) thin film on the FTO surface. The TNP film has a thickness of about 50 nm, while the TNS has thickness only about 15 nm.
S6
Figure S5: Cross-sectional SEM image of a perovskite solar cell using TiO2 nanoparticle (TNP) thin film as compact layer, showing the structure and quality of the PSC. Due to some pinholes in the perovskite capping layer, hole-transport materials (spiro-OMeTAD) might permeate to the mesoporous layer.
Figure S6: Histogram of the PCE data for PSCs using TNS film prepared from 5 min EPD as the compact layer. The PSC has a mean efficiency of 9.3% and the highest value of 10.7%.
S7
Figure S7: Photovoltaic parameters of the CH3NH3PbI3 solar cells depend on the deposition time of TNS compact layers. Every deposition condition has at least 8 devices.
Figure S8: The difference of current between forward scan and reverse scan (ΔI=Iforward-Ireverse) for the TNS/FTO and TNP/FTO films.
S8
Table S1: Photovoltaic properties of the CH3NH3PbI3 perovskite solar cells using TNS and TNP as the compact layers in the hysteresis measurement. Voc (mV)
Jsc (mA cm-2)
FF
PCE (%)
TNS, Forward
888
17.3
0.60
9.2
TNS, Reverse
917
17.5
0.67
10.7
TNP, Forward
858
19.4
0.52
8.6
TNP, Reverse
855
21.5
0.58
10.7
References (1)
Li, L.; Ma, R. Z.; Ebina, Y.; Fukuda, K.; Takada, K.; Sasaki, T. Layer-by-Layer Assembly and Spontaneous Flocculation of Oppositely Charged Oxide and Hydroxide Nanosheets into Inorganic Sandwich Layered Materials J. Am. Chem. Soc. 2007, 129, 8000–8007.
(2)
Ohwada, M.; Kimoto, K; Mizoguchi, T.; Ebina, Y.; Sasaki, T. Atomic Structure of Titania Nanosheet with Vacancies. Sci. Rep. 2013, 3, 2801.
(3)
Sasaki,
T.;
Watanabe,
M.;
Hashizume,
H.;
Yamada,
H.;
Nakazawa,
H.
Macromolecule-like Aspects for a Colloidal Suspension of an Exfoliated Titanate. Pairwise Association of Nanosheets and Dynamic Reassembling Process Initiated from It. J. Am. Chem. Soc. 1996, 118, 8329–8335. (4)
Burschka, J.; Pellet, N.; Moon, S. J.; Baker, R. H.; Gao, P.; Nazeeruddin, M. K.; Grätzel,
M.
Sequential
Deposition
as
a
Route
Perovskite-Sensitized Solar Cells Nature 2013, 499, 316–319
S9
to
High-Performance
