Evolution of Chemical Composition, Morphology, and Photovoltaic ...
Evolution of Chemical Composition, Morphology, and Photovoltaic Efficiency of CH3NH3PbI3 Perovskite under Ambient Conditions 1
Weixin Huang1,2, Joseph S. Manser1,3, Prashant V. Kamat1,2,3, and Sylwia Ptasinska1,4 Radiation Laboratory, 2Department of Chemistry and Biochemistry, 3Department of Chemical and Biomolecular Engineering, and 4Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA Supporting Information
Figure S1. X-ray photoelectron spectroscopy survey spectra (left), and high-resolution I 3d5/2 and Pb 4f spectra (right) for CH3NH3PbI3 films stored under ambient laboratory conditions for (a) 0 days and (b) 21 days. Pass energy was set at 100 eV for the survey spectra, and at 45 eV for the I 3d5/2 and Pb 4f spectra.
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Figure S2. Spectral fitting and peak assignments for CH3NH3PbI3 perovskite films exposed to ambient conditions. (a) I 3d5/2, (b) Pb 4f, (c) C 1s, and (d) O 1s. Peak assignments: (A) 619.4 ± 0.1 eV (Pb-I), (B) 138.5 ± 0.1 eV (Pb-I, Pb(OH)2), (C) 139.3 ± 0.1 eV (PbCO3), and (D) 137.8 ± 0.1 eV (PbO), (E) 285.3 ± 0.1 eV (adventitious carbon), (F) 286.6 ± 0.1 eV (CH3NH3+), (G) 288.9 eV ± 0.2 eV (PbCO3), (H) 531.1 ± 0.1 eV (PbCO3, β-PbO, SnO2), (I) 532.4 ± 0.1 eV (adventitious oxygen, Pb(OH)2), (J) 533.9 eV ± 0.1 eV (adventitious oxygen), and (K) 529.3 ± 0.2 eV (α-PbO).
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Figure S3. X-ray photoelectron spectroscopy survey spectra for PbI2 powder stored under ambient laboratory conditions for (a) 0 days and (b) 8 days. Evolutions of Pb 4f and C 1s spectra for PbI2 powder (bottom).
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Figure S4. Spectral fitting and peak assignments for PbI2 powder exposed to ambient conditions (a) C 1s, and (b) O 1s. Each spectrum is normalized with respect to y-axis: (A) 285.3 ± 0.1 eV (adventitious carbon), (B) 286.6 ± 0.1 eV (adventitious carbon), (C) 288.9 eV ± 0.2 eV (PbCO3), and (D) 531.1 ± 0.2 eV (adventitious oxygen, PbCO3, β-PbO), (E) 532.4 ± 0.1 eV (Pb(OH)2), and (F) 529.3 ± 0.2 eV (α-PbO).
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Figure S5. Summarized photovoltaic parameters for perovskite solar cells prepared from CH3NH3PbI3 films stored under ambient conditions for the specified duration (JSC – short-circuit current density, VOC – open-circuit voltage, ff – fill factor, η – power conversion efficiency). The middle line represents the median of the data set, the solid circle the mean, the lower and upper box edges are the 25th and 75th percentile, respectively, and the whiskers show the maximum and minimum value for each parameter. Red boxes are derived from reverse J-V scans (VOC to JSC), while the black boxes represent data from forward scans (JSC to VOC). The number of devices included in the statistical analysis for each data set was between 9 and 12.
Figure S6. Optical emission spectrum of fluorescent tube bulb used in the laboratory. 5
Table S1. N/Pb, I/Pb, CO32-/Pb and O529.3eV/Pb ratios for CH3NH3PbI3 films stored under ambient conditions.
Table S2. I/Pb, CO32-/Pb and O529.3eV/Pb ratios for PbI2 powder stored under ambient conditions.
Table S3. Hysteresis index for perovskite solar cells prepared from CH3NH3PbI3 films stored under ambient conditions. The average of six devices is shown along with the 95% confidence interval (α = 0.05).
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The Gibbs free energy of proposed reactions Since sample degradation is under standard state conditions of 1 atm pressure and 298 K, the Gibbs free energy change of reactions can be calculated from the standard formation Gibbs free energy of the substances. The reversible hydration and dehydration of CH3NH3PbI3 films in Steps (1) and (2) have been discussed in detailed in the literature.1-3 Additionally, the formation Gibbs free energy of hydrate, (CH3NH3)4PbI6 ·2H2O, is still unknown. Therefore, only the Gibbs free energy of proposed reactions (3) - (5) was calculated. We assume the transient state (CH3NH3)xPbI2+x is lead iodide (x=0) with lattice strain and that it has the same formation Gibbs free energy of lead iodide. Reaction (3), 2(CH3NH3)xPbI2+x + 2CO2 + O2 → 2PbCO3 + 2I2 ↑+ 2xCH3NH2 ↑ + 2xHI ↑ 2PbI2 + 2CO2 + O2 → 2PbCO3 + 2I2 ↑ (when x=0)
equivalent to
θ ∆rG(3) = 2 ∆f G (PbCO3) + 2 ∆f G (I2 (s)) - 2 ∆f G (PbI2) - 2 ∆f G (CO2) - ∆f G (O2) = 2(-626.3) + 0 – 2(-173) – 2 (-394) = -118.6 kJ mol-1
Reaction (4), equivalent to
(CH3NH3)xPbI2+x + H2O + 1/2 O2 → Pb(OH)2 + I2 ↑ + xHI ↑+ xCH3NH2 ↑ PbI2 + H2O + 1/2 O2 →Pb(OH)2 + I2 ↑ (when x=0) θ ∆rG(4) = ∆f G (Pb(OH)2) + ∆f G (I2 (s)) - ∆f G (PbI2) - ∆f G (H2O(g)) = -420.9 + 0 – (-173) –(-228.6) = -19.3 kJ mol-1
Reaction (5), Pb(OH)2 →PbO + H2O ∆rG(5) = + ∆f G (H2O(l)) - ∆f G (Pb(OH)2) = -187.9 + (-237.1) – (-420.9) = -4.13 kJ mol-1
∆f Gθ(PbO)
REFERENCES [1] Christians, J. A.; Miranda Herrera, P. A.; Kamat, P. V. Transformation of the Excited State and Photovoltaic Efficiency of CH3NH3PbI3 Perovskite upon Controlled Exposure to Humidified Air. J. Am. Chem. Soc. 2015, 137, 1530–1538.
[2] Leguy, A. M. A.; Hu, Y.; Campoy-Quiles, M.; Alonso, M. I.; Weber, O. J.; Azarhoosh, P.; Schilfgaarde, M. van; Weller, M. T.; Bein, T.; Nelson, J.; Docampo, P.; Barnes, P. R. F. Reversible Hydration of CH3NH3PbI3 in Films, Single Crystals, and Solar Cells. Chem. Mater. 2015, 27, 3397–3407. [3] Yang, J.; Siempelkamp, B. D.; Liu, D.; Kelly, T. L. An Investigation of CH3NH3PbI3 Degradation Rates and Mechanisms in Controlled Humidity Environments Using in Situ Techniques. ACS Nano 2015, 9, 1955–1963.
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Weixin Huang1,2, Joseph S. Manser1,3, Prashant V. Kamat1,2,3, and Sylwia Ptasinska1,4 Radiation Laboratory, 2Department of Chemistry and Biochemistry, 3Department of Chemical and Biomolecular Engineering, and 4Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA Supporting Information
Figure S1. X-ray photoelectron spectroscopy survey spectra (left), and high-resolution I 3d5/2 and Pb 4f spectra (right) for CH3NH3PbI3 films stored under ambient laboratory conditions for (a) 0 days and (b) 21 days. Pass energy was set at 100 eV for the survey spectra, and at 45 eV for the I 3d5/2 and Pb 4f spectra.
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Figure S2. Spectral fitting and peak assignments for CH3NH3PbI3 perovskite films exposed to ambient conditions. (a) I 3d5/2, (b) Pb 4f, (c) C 1s, and (d) O 1s. Peak assignments: (A) 619.4 ± 0.1 eV (Pb-I), (B) 138.5 ± 0.1 eV (Pb-I, Pb(OH)2), (C) 139.3 ± 0.1 eV (PbCO3), and (D) 137.8 ± 0.1 eV (PbO), (E) 285.3 ± 0.1 eV (adventitious carbon), (F) 286.6 ± 0.1 eV (CH3NH3+), (G) 288.9 eV ± 0.2 eV (PbCO3), (H) 531.1 ± 0.1 eV (PbCO3, β-PbO, SnO2), (I) 532.4 ± 0.1 eV (adventitious oxygen, Pb(OH)2), (J) 533.9 eV ± 0.1 eV (adventitious oxygen), and (K) 529.3 ± 0.2 eV (α-PbO).
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Figure S3. X-ray photoelectron spectroscopy survey spectra for PbI2 powder stored under ambient laboratory conditions for (a) 0 days and (b) 8 days. Evolutions of Pb 4f and C 1s spectra for PbI2 powder (bottom).
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Figure S4. Spectral fitting and peak assignments for PbI2 powder exposed to ambient conditions (a) C 1s, and (b) O 1s. Each spectrum is normalized with respect to y-axis: (A) 285.3 ± 0.1 eV (adventitious carbon), (B) 286.6 ± 0.1 eV (adventitious carbon), (C) 288.9 eV ± 0.2 eV (PbCO3), and (D) 531.1 ± 0.2 eV (adventitious oxygen, PbCO3, β-PbO), (E) 532.4 ± 0.1 eV (Pb(OH)2), and (F) 529.3 ± 0.2 eV (α-PbO).
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Figure S5. Summarized photovoltaic parameters for perovskite solar cells prepared from CH3NH3PbI3 films stored under ambient conditions for the specified duration (JSC – short-circuit current density, VOC – open-circuit voltage, ff – fill factor, η – power conversion efficiency). The middle line represents the median of the data set, the solid circle the mean, the lower and upper box edges are the 25th and 75th percentile, respectively, and the whiskers show the maximum and minimum value for each parameter. Red boxes are derived from reverse J-V scans (VOC to JSC), while the black boxes represent data from forward scans (JSC to VOC). The number of devices included in the statistical analysis for each data set was between 9 and 12.
Figure S6. Optical emission spectrum of fluorescent tube bulb used in the laboratory. 5
Table S1. N/Pb, I/Pb, CO32-/Pb and O529.3eV/Pb ratios for CH3NH3PbI3 films stored under ambient conditions.
Table S2. I/Pb, CO32-/Pb and O529.3eV/Pb ratios for PbI2 powder stored under ambient conditions.
Table S3. Hysteresis index for perovskite solar cells prepared from CH3NH3PbI3 films stored under ambient conditions. The average of six devices is shown along with the 95% confidence interval (α = 0.05).
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The Gibbs free energy of proposed reactions Since sample degradation is under standard state conditions of 1 atm pressure and 298 K, the Gibbs free energy change of reactions can be calculated from the standard formation Gibbs free energy of the substances. The reversible hydration and dehydration of CH3NH3PbI3 films in Steps (1) and (2) have been discussed in detailed in the literature.1-3 Additionally, the formation Gibbs free energy of hydrate, (CH3NH3)4PbI6 ·2H2O, is still unknown. Therefore, only the Gibbs free energy of proposed reactions (3) - (5) was calculated. We assume the transient state (CH3NH3)xPbI2+x is lead iodide (x=0) with lattice strain and that it has the same formation Gibbs free energy of lead iodide. Reaction (3), 2(CH3NH3)xPbI2+x + 2CO2 + O2 → 2PbCO3 + 2I2 ↑+ 2xCH3NH2 ↑ + 2xHI ↑ 2PbI2 + 2CO2 + O2 → 2PbCO3 + 2I2 ↑ (when x=0)
equivalent to
θ ∆rG(3) = 2 ∆f G (PbCO3) + 2 ∆f G (I2 (s)) - 2 ∆f G (PbI2) - 2 ∆f G (CO2) - ∆f G (O2) = 2(-626.3) + 0 – 2(-173) – 2 (-394) = -118.6 kJ mol-1
Reaction (4), equivalent to
(CH3NH3)xPbI2+x + H2O + 1/2 O2 → Pb(OH)2 + I2 ↑ + xHI ↑+ xCH3NH2 ↑ PbI2 + H2O + 1/2 O2 →Pb(OH)2 + I2 ↑ (when x=0) θ ∆rG(4) = ∆f G (Pb(OH)2) + ∆f G (I2 (s)) - ∆f G (PbI2) - ∆f G (H2O(g)) = -420.9 + 0 – (-173) –(-228.6) = -19.3 kJ mol-1
Reaction (5), Pb(OH)2 →PbO + H2O ∆rG(5) = + ∆f G (H2O(l)) - ∆f G (Pb(OH)2) = -187.9 + (-237.1) – (-420.9) = -4.13 kJ mol-1
∆f Gθ(PbO)
REFERENCES [1] Christians, J. A.; Miranda Herrera, P. A.; Kamat, P. V. Transformation of the Excited State and Photovoltaic Efficiency of CH3NH3PbI3 Perovskite upon Controlled Exposure to Humidified Air. J. Am. Chem. Soc. 2015, 137, 1530–1538.
[2] Leguy, A. M. A.; Hu, Y.; Campoy-Quiles, M.; Alonso, M. I.; Weber, O. J.; Azarhoosh, P.; Schilfgaarde, M. van; Weller, M. T.; Bein, T.; Nelson, J.; Docampo, P.; Barnes, P. R. F. Reversible Hydration of CH3NH3PbI3 in Films, Single Crystals, and Solar Cells. Chem. Mater. 2015, 27, 3397–3407. [3] Yang, J.; Siempelkamp, B. D.; Liu, D.; Kelly, T. L. An Investigation of CH3NH3PbI3 Degradation Rates and Mechanisms in Controlled Humidity Environments Using in Situ Techniques. ACS Nano 2015, 9, 1955–1963.
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