Supporting Information Solution Processed Air Stable Mesoscopic ...
Supporting Information
Solution Processed Air Stable Mesoscopic Selenium Solar Cells Menghua Zhu 1,2, Feng Hao2, Lin Ma2, Tze-Bin Song2, Claire E. Miller2, Michael R. Wasielewski 2, Xin Li1* and Mercouri G. Kanatzidis2* 1
School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150090, China. *E-mail address: [email protected] 2
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA. *E-mail: [email protected]
Experimental section Materials. Unless stated otherwise, all materials were purchased from Sigma-Aldrich and used as received. Selenium(99.99%) was purchased from American Elements inc. Selenium solution was prepared by 240mg selenium and 1 mL hydrazine and EDA mixture solvents (EDA volume from 10 µL to 100 µL ), keep the solution stirring at 70 o C for 30min. Caution: hydrazine is highly toxic and reactive and must be handled using appropriate protective equipment to prevent physical contact with either vapor or liquid. Caution: hydrazine is highly toxic and reactive and must be handled using appropriate protective equipment to prevent physical contact with either vapor or liquid. Caution: hydrazine is highly toxic and reactive and must be handled using appropriate protective equipment to prevent physical contact with either vapor or liquid. Solar cell fabrication. FTO-coated glass substrates (Tec15, Hartford Glass Co. Inc.) was patterned by etching with Zn metal powder and 2 M HCl diluted in deionized water. The substrates were then cleaned by ultrasonication with detergent, rinsed with deionized water, acetone and ethanol, and dried with clean dry air. A compact layer of TiO 2 (~30nm in thickness) was prepared on cleaned fluorine-doped tin oxide glass (FTO) by spin-coating titanium isopropylate (TTIP) solution, A 200-300nm thick mesoporous TiO 2 (mp-TiO 2) film was spin-coated onto the compact TiO 2 (cp-TiO 2)/fluorine doped Tin Oxide (FTO) substrate using home-made TiO 2 pastes and calcined at 500 o C for 30min. For depositing a selenium layer, selenium solution was spin-coated onto mp-TiO 2 /cp-TiO 2 /FTO substrate from precursor solution at spin rates of 2000 rpm for 30s to form a selenium film. The selenium film was kept at 80 oC for 10min, and then heated up to 200 oC for 3 min to complete the crystallization process. Subsequently, the PTAA (EM index, Mw = 17,500 g mol-1)/toluene(15 mg/1 ml) solution with added 13.6 μL Li-bis(trifluoromethanesulfonyl) imide (Li-TFSI)/acetonitrile (28.3 mg/1 ml) and 6.8 μL tBP as hole transport materials was spin-coated on Se/mp-TiO 2/cp-TiO 2/FTO substrate at 3,000 r.p.m. for 30 s. Finally, an 80 nm Au layer was prepared by thermal vacuum evaporation. The active area of the solar cell was fixed at 0.12 cm 2. Characterization. The XRD spectra of the prepared films were measured using a Rigaku SmartLab X-ray diffractometer, and XRD experiments of the powder isolated as an intermediate phase were performed using a Rigaku Ultima IV with an X -ray tube (Cu K α 1
λ=1.5406Å). Ultraviolet-visible absorption spectra were recorded on a Shimadzu UV-3101 spectrophotometer in the 200-800 nm wavelength range at room temperature. BaSO4 was used as a non-absorbing reflectance reference. SEM measurements were performed with a Hitachi SU8030 scanning electron microscope equipped with an Oxford X-max 80 SDD EDS detector. Data were acquired with an accelerating voltage of 15 kV. Electrochemical determination of the conduction band potential. Cyclic voltammetry (CV) curves were measured with an electrochemical workstation (CHI660E electrochemical analyzer, CH Instruments, Inc., USA). J-V characteristics were measured using a solar simulator (xenon arc lamp of a Spectra-Nova Class A) under AM 1.5G light (100 mW cm -2) illumination, calibrated with Si-reference cell certified by the NREL. A Keithley 2400 source meter was used for electrical characterization. J-V curves for all devices were measured by masking the active area with a metal mask 8 mm 2 in area. Internal power conversion efficiencies (IPCE)s were measured using an Oriel model QE-PV-SI instrument equipped with a NIST-certified Si diode. Monochromatic light was generated from an Oriel 300 W lamp. Transient absorption spectroscopy. Visible/near-infrared femtosecond transient absorption spectroscopy was performed using an instrument previously described. 1 Briefly, the approximately 120 fs, 1 kHz output of a commercial Ti:sapphire oscillator/amplifier (Tsunami/Spitfire, SpectraPhysics) was split to seed and pump a laboratory constructed optical parametric amplifier used to generate the 525 nm excitation (“pump”) beam, and to generate a femtosecond continuum probe, by using either a sapphire crystal for the visible range or a proprietary crystal for the near-infrared (NIR) spectral region (Ultrafast Systems, LLC). Transient spectra were collected by using customized commercial detectors (Helios, Ultrafast Systems,
LLC).
Table S1 Summary of selenium based solar cells and there corresponding process conditions with device characteristics (PCE, %). Method
ETL layer
HTL layer
V OC(V)
Solution
PTAA
0.66
Vacuum
Compact TiO2/ mesoTiO2 Te
/
Vacuum
TiO2
Vacuum
Compact TiO2/meso TiO2
JSC(mA -2 cm )
FF
PCE （%）
Reference
9.1
0.57
3.52
Current Work
0.54
10.9
0.56
3.3
6
/
0.88
10.08
0.53
5.01
7
P3HT/ PEDOT: PSS
0.71
9.71
0.38
2.63
8
0.53
3.0
9
Electroche Compact / 0.65 8.7 mical TiO2/meso deposition TiO2 ETL: electron transport material; HTL: hole transport material
2
Table S2 TA kinetics fitting results at 658 nm of Se films. Time
Se on Al2O3
Se on TiO2
1
2.2±0.3 ps (29%)
1.8±0.2 ps (66%)
2
25±3 ps (28%)
56.4±0.2 ps(34%)
3
260±30 ps (23%)
/
4
17±3 ns (20%)
/
Figure S1. XRD pattern of the selenium film after sintering 180℃-200℃coating on glass/FTO/blTiO2,mp-TiO2 substrate, The inset shows a image of a surface consisting of a glass/FTO/bl -TiO2, mp-TiO2-Se layer /Se overlayer with different sintering temperature.
Figure S2. Cyclic voltammogram of solution processed selenium film on FTO cast onto a Ag/AgCl electrode in potassium phosphate monobasic/sodium hydroxide/water. Scan rate = 100 mV/s. (counter electrode: Pt )
3
Figure S3. Long-term stability of the cell stored in ambient atmosphere at room temperature without encapsulation and measured under one sun illumination.
Figure S4. Transient absorption spectra of Se on TiO 2 film under excitation at 525 nm.
References （1）Young, R. M.; Dyar, S. M.; Barnes, J. C.; Juríček, M.; Stoddart, J. F. ; Co, D. T.; Wasielewski, M. R. Ultrafast conformational dynamics of electron transfer in exbox perylene. J. Phys. Chem. A. 2013, 117 (47), 12438-12448.
4
Solution Processed Air Stable Mesoscopic Selenium Solar Cells Menghua Zhu 1,2, Feng Hao2, Lin Ma2, Tze-Bin Song2, Claire E. Miller2, Michael R. Wasielewski 2, Xin Li1* and Mercouri G. Kanatzidis2* 1
School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150090, China. *E-mail address: [email protected] 2
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA. *E-mail: [email protected]
Experimental section Materials. Unless stated otherwise, all materials were purchased from Sigma-Aldrich and used as received. Selenium(99.99%) was purchased from American Elements inc. Selenium solution was prepared by 240mg selenium and 1 mL hydrazine and EDA mixture solvents (EDA volume from 10 µL to 100 µL ), keep the solution stirring at 70 o C for 30min. Caution: hydrazine is highly toxic and reactive and must be handled using appropriate protective equipment to prevent physical contact with either vapor or liquid. Caution: hydrazine is highly toxic and reactive and must be handled using appropriate protective equipment to prevent physical contact with either vapor or liquid. Caution: hydrazine is highly toxic and reactive and must be handled using appropriate protective equipment to prevent physical contact with either vapor or liquid. Solar cell fabrication. FTO-coated glass substrates (Tec15, Hartford Glass Co. Inc.) was patterned by etching with Zn metal powder and 2 M HCl diluted in deionized water. The substrates were then cleaned by ultrasonication with detergent, rinsed with deionized water, acetone and ethanol, and dried with clean dry air. A compact layer of TiO 2 (~30nm in thickness) was prepared on cleaned fluorine-doped tin oxide glass (FTO) by spin-coating titanium isopropylate (TTIP) solution, A 200-300nm thick mesoporous TiO 2 (mp-TiO 2) film was spin-coated onto the compact TiO 2 (cp-TiO 2)/fluorine doped Tin Oxide (FTO) substrate using home-made TiO 2 pastes and calcined at 500 o C for 30min. For depositing a selenium layer, selenium solution was spin-coated onto mp-TiO 2 /cp-TiO 2 /FTO substrate from precursor solution at spin rates of 2000 rpm for 30s to form a selenium film. The selenium film was kept at 80 oC for 10min, and then heated up to 200 oC for 3 min to complete the crystallization process. Subsequently, the PTAA (EM index, Mw = 17,500 g mol-1)/toluene(15 mg/1 ml) solution with added 13.6 μL Li-bis(trifluoromethanesulfonyl) imide (Li-TFSI)/acetonitrile (28.3 mg/1 ml) and 6.8 μL tBP as hole transport materials was spin-coated on Se/mp-TiO 2/cp-TiO 2/FTO substrate at 3,000 r.p.m. for 30 s. Finally, an 80 nm Au layer was prepared by thermal vacuum evaporation. The active area of the solar cell was fixed at 0.12 cm 2. Characterization. The XRD spectra of the prepared films were measured using a Rigaku SmartLab X-ray diffractometer, and XRD experiments of the powder isolated as an intermediate phase were performed using a Rigaku Ultima IV with an X -ray tube (Cu K α 1
λ=1.5406Å). Ultraviolet-visible absorption spectra were recorded on a Shimadzu UV-3101 spectrophotometer in the 200-800 nm wavelength range at room temperature. BaSO4 was used as a non-absorbing reflectance reference. SEM measurements were performed with a Hitachi SU8030 scanning electron microscope equipped with an Oxford X-max 80 SDD EDS detector. Data were acquired with an accelerating voltage of 15 kV. Electrochemical determination of the conduction band potential. Cyclic voltammetry (CV) curves were measured with an electrochemical workstation (CHI660E electrochemical analyzer, CH Instruments, Inc., USA). J-V characteristics were measured using a solar simulator (xenon arc lamp of a Spectra-Nova Class A) under AM 1.5G light (100 mW cm -2) illumination, calibrated with Si-reference cell certified by the NREL. A Keithley 2400 source meter was used for electrical characterization. J-V curves for all devices were measured by masking the active area with a metal mask 8 mm 2 in area. Internal power conversion efficiencies (IPCE)s were measured using an Oriel model QE-PV-SI instrument equipped with a NIST-certified Si diode. Monochromatic light was generated from an Oriel 300 W lamp. Transient absorption spectroscopy. Visible/near-infrared femtosecond transient absorption spectroscopy was performed using an instrument previously described. 1 Briefly, the approximately 120 fs, 1 kHz output of a commercial Ti:sapphire oscillator/amplifier (Tsunami/Spitfire, SpectraPhysics) was split to seed and pump a laboratory constructed optical parametric amplifier used to generate the 525 nm excitation (“pump”) beam, and to generate a femtosecond continuum probe, by using either a sapphire crystal for the visible range or a proprietary crystal for the near-infrared (NIR) spectral region (Ultrafast Systems, LLC). Transient spectra were collected by using customized commercial detectors (Helios, Ultrafast Systems,
LLC).
Table S1 Summary of selenium based solar cells and there corresponding process conditions with device characteristics (PCE, %). Method
ETL layer
HTL layer
V OC(V)
Solution
PTAA
0.66
Vacuum
Compact TiO2/ mesoTiO2 Te
/
Vacuum
TiO2
Vacuum
Compact TiO2/meso TiO2
JSC(mA -2 cm )
FF
PCE （%）
Reference
9.1
0.57
3.52
Current Work
0.54
10.9
0.56
3.3
6
/
0.88
10.08
0.53
5.01
7
P3HT/ PEDOT: PSS
0.71
9.71
0.38
2.63
8
0.53
3.0
9
Electroche Compact / 0.65 8.7 mical TiO2/meso deposition TiO2 ETL: electron transport material; HTL: hole transport material
2
Table S2 TA kinetics fitting results at 658 nm of Se films. Time
Se on Al2O3
Se on TiO2
1
2.2±0.3 ps (29%)
1.8±0.2 ps (66%)
2
25±3 ps (28%)
56.4±0.2 ps(34%)
3
260±30 ps (23%)
/
4
17±3 ns (20%)
/
Figure S1. XRD pattern of the selenium film after sintering 180℃-200℃coating on glass/FTO/blTiO2,mp-TiO2 substrate, The inset shows a image of a surface consisting of a glass/FTO/bl -TiO2, mp-TiO2-Se layer /Se overlayer with different sintering temperature.
Figure S2. Cyclic voltammogram of solution processed selenium film on FTO cast onto a Ag/AgCl electrode in potassium phosphate monobasic/sodium hydroxide/water. Scan rate = 100 mV/s. (counter electrode: Pt )
3
Figure S3. Long-term stability of the cell stored in ambient atmosphere at room temperature without encapsulation and measured under one sun illumination.
Figure S4. Transient absorption spectra of Se on TiO 2 film under excitation at 525 nm.
References （1）Young, R. M.; Dyar, S. M.; Barnes, J. C.; Juríček, M.; Stoddart, J. F. ; Co, D. T.; Wasielewski, M. R. Ultrafast conformational dynamics of electron transfer in exbox perylene. J. Phys. Chem. A. 2013, 117 (47), 12438-12448.
4
