High-efficiency two-dimensional Ruddlesden–Popper perovskite solar cells

Journal name:
Nature
Volume:
536,
Pages:
312–316
Date published:
DOI:
doi:10.1038/nature18306
Received
Accepted
Published online

Three-dimensional organic–inorganic perovskites have emerged as one of the most promising thin-film solar cell materials owing to their remarkable photophysical properties1, 2, 3, 4, 5, which have led to power conversion efficiencies exceeding 20 per cent6, 7, with the prospect of further improvements towards the Shockley–Queisser limit for a single‐junction solar cell (33.5 per cent)8. Besides efficiency, another critical factor for photovoltaics and other optoelectronic applications is environmental stability and photostability under operating conditions9, 10, 11, 12, 13, 14, 15. In contrast to their three-dimensional counterparts, Ruddlesden–Popper phases—layered two-dimensional perovskite films—have shown promising stability, but poor efficiency at only 4.73 per cent13, 16, 17. This relatively poor efficiency is attributed to the inhibition of out-of-plane charge transport by the organic cations, which act like insulating spacing layers between the conducting inorganic slabs. Here we overcome this issue in layered perovskites by producing thin films of near-single-crystalline quality, in which the crystallographic planes of the inorganic perovskite component have a strongly preferential out-of-plane alignment with respect to the contacts in planar solar cells to facilitate efficient charge transport. We report a photovoltaic efficiency of 12.52 per cent with no hysteresis, and the devices exhibit greatly improved stability in comparison to their three-dimensional counterparts when subjected to light, humidity and heat stress tests. Unencapsulated two-dimensional perovskite devices retain over 60 per cent of their efficiency for over 2,250 hours under constant, standard (AM1.5G) illumination, and exhibit greater tolerance to 65 per cent relative humidity than do three-dimensional equivalents. When the devices are encapsulated, the layered devices do not show any degradation under constant AM1.5G illumination or humidity. We anticipate that these results will lead to the growth of single-crystalline, solution-processed, layered, hybrid, perovskite thin films, which are essential for high-performance opto-electronic devices with technologically relevant long-term stability.

At a glance

Figures

  1. Crystal structure and thin-film characterization of layered perovskites.
    Figure 1: Crystal structure and thin-film characterization of layered perovskites.

    a, The crystal structure of the Ruddlesden–Popper (BA)2(MA)2Pb3I10 and (BA)2(MA)3Pb4I13 layered perovskites, depicted as n polyhedral blocks, where n refers to the number of layers; the BA spacer layers are depicted as space-fill models to illustrate the termination of the perovskite layers. b, Photos of (BA)2(MA)3Pb4I13 thin films cast from room temperature (RT) to 150 °C. The film colour gets darker with increasing temperature. c, Comparison of GIXRD spectra for room-temperature-cast (black dashed line) and hot-cast (red line) (BA)2(MA)3Pb4I13 films, respectively. The (111), (202) and (313) labels correspond to preferred diffraction planes. d, The full-width at half-maximum (FWHM) of GIXRD peak (202) as a function of temperature from room temperature to 150 °C. The inset shows the FWHM for each plane indicated in c. e, Absorbance of a 370-nm thin film (n = 4) measured in an integrating sphere (grey circles) and with confocal microscopy (black line), along with the photoluminescence spectra for excitation at 1.96 eV (red line). a.u., arbitrary units.

  2. GIWAXS images and structure orientation.
    Figure 2: GIWAXS images and structure orientation.

    a, b, GIWAXS maps for polycrystalline room-temperature-cast (a) and hot-cast (b) near-single-crystalline (BA)2(MA)3Pb4I13 perovskite films with Miller indices of the most prominent peaks shown in white. Colour scale is proportional to X-ray scattering intensity. c, Schematic representation of the (101) orientation, along with the and (202) planes of a 2D perovskite crystal, consistent with the GIWAXS data.

  3. Solar cell architecture and characterization.
    Figure 3: Solar cell architecture and characterization.

    a, Experimental (red line) and simulated (black dashed line) current-density–voltage (JV) curves under an AM.1.5G solar simulator for planar devices using 2D (BA)2(MA)3Pb4I13 perovskites as the absorbing layer at optimized thickness (230 nm). The inset shows the device architecture. Al, aluminium; PCBM, [6,6]-phenyl-C61-butyric acid methyl ester; PEDOT:PSS, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate; FTO, fluorine-doped tin oxide. b, External quantum efficiency (EQE; red circles and line) and integrated short-circuit current density (JSC; blue dashed line) as a function of wavelength. c, d, JV curves for hysteresis tests under AM1.5G illumination measured with the voltage scanned in opposite directions (c) and with varying voltage delay times (d). e, Histogram of (BA)2(MA)3Pb4I13 device power conversion efficiency (PCE) over 50 measured devices, fitted with a Gaussian distribution (red line). f, Capacitance–d.c. bias (CV) curves (red squares) for a typical device detected by a small-amplitude a.c. field (peak-to-peak voltage VPP = 20 mV) at an a.c. frequency of 100 kHz, and the corresponding charge density profile (blue squares) extracted from the CV curve.

  4. Stability measurements on planar solar cells.
    Figure 4: Stability measurements on planar solar cells.

    a, c, Photostability tests under constant AM1.5G illumination for 2D ((BA)2(MA)3Pb4I13; red) and 3D (MAPbI3; blue) perovskite devices without (a) and with (c) encapsulation. b, d, Humidity stability tests under 65% relative humidity at in a humidity chamber for 2D ((BA)2(MA)3Pb4I13; red) and 3D (MAPbI3; blue) perovskite devices without (b) and with (d) encapsulation. PCE, power conversion efficiency; a.u., arbitrary units.

  5. Layered perovskite thin-film morphology and device performance.
    Extended Data Fig. 1: Layered perovskite thin-film morphology and device performance.

    a, b, AFM images of surface morphology for room-temperature-cast (a) and hot-cast (b) films. Scale bars, 400 nm. c, d, SEM images of topography for room-temperature-cast (c) and hot-cast (d) films. Scale bars, 1 μm. e, JV curve of Pb4I13 with C60 as a contact modification candidate shows the enhancement of VOC from 0.9 V to 1.055 V with the same device architecture. f, JV curve for the (BA)2(MA)3Pb4I13 device using the room-temperature (RT) spin-cast method. FF, fill factor.

  6. Absorption spectroscopy of layered 2D perovskites.
    Extended Data Fig. 2: Absorption spectroscopy of layered 2D perovskites.

    ac, Local optical absorption characteristics of thin films using reflection/transmission experimental methods (see also refs 34, 35 for details of the modelling): results of the fitting of the reflection (R) and transmission (T) data (a); absolute absorption cross-section (b); and real (n; red line) and imaginary (k; black line) parts of the refractive index (c). d, Absorbance of thin films (grey circles) compared to that of optimized solar cells (red squares) measured using integrating sphere techniques (see details in ref. 36).

  7. DFT computation.
    Extended Data Fig. 3: DFT computation.

    a, b, Electronic band structures of (BA)2PbI4 (n = 1; a) and (BA)2(MA)2Pb3I10 (n = 3; b) calculated using DFT with a local-density approximation, including the spin–orbit coupling and a bandgap correction computed using the HSE (Heyd–Scuseria–Ernzerhof) functional. The energy levels are referenced to the valence band maximum.

  8. Device performance of (BA)2(MA)2Pb3I10.
    Extended Data Fig. 4: Device performance of (BA)2(MA)2Pb3I10.

    a, JV curve and device parameters. b, EQE (red circles) and integrated JSC from EQE (blue dashed line).

  9. Dark current transient and mobility.
    Extended Data Fig. 5: Dark current transient and mobility.

    The dark current transient (ΔJ/J0), measured using the CELIV technique, for a hot-cast (red) and a room-temperature-cast (‘As cast’, black) device, and the mobility value (μ) in each case.

  10. Device PCE as a function of thin-film thickness for the layered Pb4I13 perovskite.
    Extended Data Fig. 6: Device PCE as a function of thin-film thickness for the layered Pb4I13 perovskite.
  11. Hysteresis tests for 2D pervoskite devices.
    Extended Data Fig. 7: Hysteresis tests for 2D pervoskite devices.

    ad, Tests with different bias sweep directions (a; (C/C0)−2 as function of DC bias, where C0 is the capacitance of a geometric capacitor), and after 10 h (b), 1,000 h (c) and 2,250 h (d) of constant illumination. The red and blue arrows indicate the forward and reverse sweep directions.

  12. Simulation results and comparison of room-temperature-cast and hot-cast methods.
    Extended Data Fig. 8: Simulation results and comparison of room-temperature-cast and hot-cast methods.

    a, Experimental (‘Expr.’) JV characteristics of room-temperature-cast (‘As cast’) and hot-cast methods and corresponding simulation (‘Sim.’) results. The hot-cast method shows a current density with a larger magnitude and higher fill factor (area below the JV curve). b, Integrated recombination inside three layers of a solar cell. Peak recombination shifts toward the PCBM/perovskite interface because the barrier for generated carriers is less in the hot-cast case than in the room-temperature-cast case. c, d, Energy band diagram of hot-cast (c) and room-temperature-cast (d) methods. Generated carriers face a lower barrier in the hot-cast case, especially close to the PEDOT/perovskite interface. EC, conduction band; EV, valence band; EFN, electron quasi-Fermi level; EFP, hole quasi-Fermi level.

  13. Heat stress tests.
    Extended Data Fig. 9: Heat stress tests.

    a, b, Spectra of 2D (a) and 3D (b) perovskite thin films under 80 °C in darkness after the lengths of time indicated (spectra are offset for clarity; ‘ref.’ refers to freshly made thin film, measured after 0 h of heat stressing). c, Ratio of the PbI2 (2θ = 12.7°) and perovskite (2θ = 14.2°) main peaks in the spectra in a and b for the two perovskite materials (2D, blue; 3D, red) over 30 h of heating at 80 °C.

References

  1. Yaffe, O. et al. Excitons in ultrathin organic-inorganic perovskite crystals. Phys. Rev. B 92, 045414 (2015)
  2. Wang, G. et al. Wafer-scale growth of large arrays of perovskite microplate crystals for functional electronics and optoelectronics. Sci. Adv. 1, e1500613 (2015)
  3. de Quilettes, D. W. et al. Impact of microstructure on local carrier lifetime in perovskite solar cells. Science 348, 683686 (2015)
  4. Yin, W.-J., Shi, T. & Yan, Y. Unique properties of halide perovskites as possible origins of the superior solar cell performance. Adv. Mater. 26, 46534658 (2014)
  5. Stranks, S. D. et al. Electron-hole diffusion lengths exceeding 1 micrometer in an organometal trihalide perovskite absorber. Science 342, 341344 (2013)
  6. Saliba, M. et al. A molecularly engineered hole-transporting material for efficient perovskite solar cells. Nat. Energy 1, 15017 (2016)
  7. Yang, W. S. et al. High-performance photovoltaic perovskite layers fabricated through intramolecular exchange. Science 348, 12341237 (2015)
  8. Shockley, W. & Queisser, H. J. Detailed balance limit of efficiency of p-n junction solar cells. J. Appl. Phys. 32, 510519 (1961)
  9. You, J. et al. Improved air stability of perovskite solar cells via solution-processed metal oxide transport layers. Nat. Nanotechnol. 11, 7581 (2016)
  10. Li, X. et al. Improved performance and stability of perovskite solar cells by crystal crosslinking with alkylphosphonic acid ω-ammonium chlorides. Nat. Chem. 7, 703711 (2015)
  11. Kaltenbrunner, M. et al. Flexible high power-per-weight perovskite solar cells with chromium oxide–metal contacts for improved stability in air. Nat. Mater. 14, 10321039 (2015)
  12. Han, Y. et al. Degradation observations of encapsulated planar CH3NH3PbI3 perovskite solar cells at high temperatures and humidity. J. Mater. Chem. A Mater. Energy Sustain. 3, 81398147 (2015)
  13. Smith, I. C., Hoke, E. T., Solis-Ibarra, D., McGehee, M. D. & Karunadasa, H. I. A layered hybrid perovskite solar-cell absorber with enhanced moisture stability. Angew. Chem. Int. Ed. 53, 1123211235 (2014)
  14. Noh, J. H., Im, S. H., Heo, J. H., Mandal, T. N. & Seok, S. I. Chemical management for colorful, efficient, and stable inorganic–organic hybrid nanostructured solar cells. Nano Lett. 13, 17641769 (2013)
  15. Leijtens, T. et al. Overcoming ultraviolet light instability of sensitized TiO2 with meso-superstructured organometal tri-halide perovskite solar cells. Nat. Commun. 4, 2885 (2013)
  16. Cao, D. H., Stoumpos, C. C., Farha, O. K., Hupp, J. T. & Kanatzidis, M. G. 2D homologous perovskites as light-absorbing materials for solar cell applications. J. Am. Chem. Soc. 137, 78437850 (2015)
  17. Kagan, C. R., Mitzi, D. B. & Dimitrakopoulos, C. D. Organic-inorganic hybrid materials as semiconducting channels in thin-film field-effect transistors. Science 286, 945947 (1999)
  18. Nie, W. et al. High-efficiency solution-processed perovskite solar cells with millimeter-scale grains. Science 347, 522525 (2015)
  19. Stoumpos, C. C. et al. Ruddlesden–Popper hybrid lead iodide perovskite 2D homologous semiconductors. Chem. Mater. 28, 28522867 (2016)
  20. Sadhanala, A. et al. Preparation of single-phase films of CH3NH3Pb(I1 − xBrx)3 with sharp optical band edges. J. Phys. Chem. Lett. 5, 25012505 (2014)
  21. Liang, P.-W. et al. Additive enhanced crystallization of solution-processed perovskite for highly efficient planar-heterojunction solar cells. Adv. Mater. 26, 37483754 (2014)
  22. Jeon, Y.-J. et al. Planar heterojunction perovskite solar cells with superior reproducibility. Sci. Rep. 4, 6953 (2014)
  23. Tress, W. et al. Understanding the rate-dependent JV hysteresis, slow time component, and aging in CH3NH3PbI3 perovskite solar cells: the role of a compensated electric field. Energy Environ. Sci. 8, 9951004 (2015)
  24. Unger, E. L. et al. Hysteresis and transient behavior in current–voltage measurements of hybrid-perovskite absorber solar cells. Energy Environ. Sci. 7, 36903698 (2014)
  25. Snaith, H. J. et al. Anomalous hysteresis in perovskite solar cells. J. Phys. Chem. Lett. 5, 15111515 (2014)
  26. Wang, W. et al. Device characteristics of CZTSSe thin-film solar cells with 12.6% efficiency. Adv. Energy Mater. 4, 1301465 (2014)
  27. Decock, K. et al. Defect distributions in thin film solar cells deduced from admittance measurements under different bias voltages. J. Appl. Phys. 110, 063722 (2011)
  28. Hegedus, S. S. & Shafarman, W. N. Thin-film solar cells: device measurements and analysis. Prog. Photovolt. Res. Appl. 12, 155176 (2004)
  29. Eisenbarth, T., Unold, T., Caballero, R., Kaufmann, C. A. & Schock, H.-W. Interpretation of admittance, capacitance-voltage, and current-voltage signatures in Cu(In,Ga)Se2 thin film solar cells. J. Appl. Phys. 107, 034509 (2010)
  30. Chen, W. et al. Efficient and stable large-area perovskite solar cells with inorganic charge extraction layers. Science 350, 944948 (2015)
  31. Mei, A. et al. A hole-conductor–free, fully printable mesoscopic perovskite solar cell with high stability. Science 345, 295298 (2014)
  32. Tsai, H. et al. Optimizing composition and morphology for large-grain perovskite solar cells via chemical control. Chem. Mater. 27, 55705576 (2015)
  33. Gelderman, K., Lee, L. & Donne, S. W. Flat-band potential of a semiconductor: using the Mott–Schottky equation. J. Chem. Educ. 84, 685688 (2007)
  34. Schulz, P. et al. Interface energetics in organo-metal halide perovskite-based photovoltaic cells. Energy Environ. Sci. 7, 13771381 (2014)
  35. Brivio, F., Walker, A. B. & Walsh, A. Structural and electronic properties of hybrid perovskites for high-efficiency thin-film photovoltaics from first-principles. APL Mater. 1, 042111 (2013)
  36. Trukhanov, V. A., Bruevich, V. V. & Paraschuk, D. Y. Effect of doping on performance of organic solar cells. Phys. Rev. B 84, 205318 (2011)

Download references

Author information

  1. These authors contributed equally to this work.

    • Hsinhan Tsai &
    • Wanyi Nie

Affiliations

  1. Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

    • Hsinhan Tsai,
    • Wanyi Nie,
    • Jean-Christophe Blancon,
    • Amanda J. Neukirch,
    • Jared J. Crochet,
    • Sergei Tretiak,
    • Gautam Gupta &
    • Aditya D. Mohite
  2. Department of Materials Science and Nanoengineering, Rice University, Houston, Texas 77005, USA

    • Hsinhan Tsai,
    • Rafael Verduzco,
    • Jun Lou &
    • Pulickel M. Ajayan
  3. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA

    • Constantinos C. Stoumpos &
    • Mercouri G. Kanatzidis
  4. Department of Materials Science, Northwestern University, Evanston, Illinois 60208, USA

    • Constantinos C. Stoumpos,
    • Boris Harutyunyan,
    • Michael J. Bedzyk &
    • Mercouri G. Kanatzidis
  5. Engineering and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208, USA

    • Constantinos C. Stoumpos,
    • Boris Harutyunyan,
    • Michael J. Bedzyk &
    • Mercouri G. Kanatzidis
  6. School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA

    • Reza Asadpour &
    • Muhammad A. Alam
  7. Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, USA

    • Rafael Verduzco
  8. Fonctions Optiques pour les Technologies de l’Information, FOTON UMR 6082, CNRS, INSA de Rennes, 35708 Rennes, France

    • Laurent Pedesseau &
    • Jacky Even

Contributions

A.D.M., H.T., W.N. and M.G.K. conceived the idea. H.T., W.N. and A.D.M. designed the experiments, analysed the data and wrote the paper. H.T. fabricated the devices along with W.N. and performed the measurements. J.-C.B. performed optical spectroscopy measurements and analysed the data under the supervision of J.J.C. C.C.S. synthesized the layered perovskites under the supervision of M.G.K. and co-wrote the paper. R.V. arranged the synchrotron experiments data, and B.H. and M.J.B. analysed and indexed the synchrotron XRD data along with M.G.K. J.E., G.G., L.P. and S.T. performed the molecular dynamics simulations. J.E. analysed the data and provided insight in writing the paper. G.G., J.L. and P.M.A. provided insights into the crystal growth of layered perovskites. R.A. and M.A.A. performed the device simulations. A.J.N. performed DFT calculations on layered perovskites under the supervision of S.T. All authors discussed the results and wrote the paper.

Competing financial interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to:

Reviewer Information

Nature thanks H. Snaith and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author details

Extended data figures and tables

Extended Data Figures

  1. Extended Data Figure 1: Layered perovskite thin-film morphology and device performance. (743 KB)

    a, b, AFM images of surface morphology for room-temperature-cast (a) and hot-cast (b) films. Scale bars, 400 nm. c, d, SEM images of topography for room-temperature-cast (c) and hot-cast (d) films. Scale bars, 1 μm. e, JV curve of Pb4I13 with C60 as a contact modification candidate shows the enhancement of VOC from 0.9 V to 1.055 V with the same device architecture. f, JV curve for the (BA)2(MA)3Pb4I13 device using the room-temperature (RT) spin-cast method. FF, fill factor.

  2. Extended Data Figure 2: Absorption spectroscopy of layered 2D perovskites. (208 KB)

    ac, Local optical absorption characteristics of thin films using reflection/transmission experimental methods (see also refs 34, 35 for details of the modelling): results of the fitting of the reflection (R) and transmission (T) data (a); absolute absorption cross-section (b); and real (n; red line) and imaginary (k; black line) parts of the refractive index (c). d, Absorbance of thin films (grey circles) compared to that of optimized solar cells (red squares) measured using integrating sphere techniques (see details in ref. 36).

  3. Extended Data Figure 3: DFT computation. (124 KB)

    a, b, Electronic band structures of (BA)2PbI4 (n = 1; a) and (BA)2(MA)2Pb3I10 (n = 3; b) calculated using DFT with a local-density approximation, including the spin–orbit coupling and a bandgap correction computed using the HSE (Heyd–Scuseria–Ernzerhof) functional. The energy levels are referenced to the valence band maximum.

  4. Extended Data Figure 4: Device performance of (BA)2(MA)2Pb3I10. (202 KB)

    a, JV curve and device parameters. b, EQE (red circles) and integrated JSC from EQE (blue dashed line).

  5. Extended Data Figure 5: Dark current transient and mobility. (194 KB)

    The dark current transient (ΔJ/J0), measured using the CELIV technique, for a hot-cast (red) and a room-temperature-cast (‘As cast’, black) device, and the mobility value (μ) in each case.

  6. Extended Data Figure 6: Device PCE as a function of thin-film thickness for the layered Pb4I13 perovskite. (167 KB)
  7. Extended Data Figure 7: Hysteresis tests for 2D pervoskite devices. (330 KB)

    ad, Tests with different bias sweep directions (a; (C/C0)−2 as function of DC bias, where C0 is the capacitance of a geometric capacitor), and after 10 h (b), 1,000 h (c) and 2,250 h (d) of constant illumination. The red and blue arrows indicate the forward and reverse sweep directions.

  8. Extended Data Figure 8: Simulation results and comparison of room-temperature-cast and hot-cast methods. (331 KB)

    a, Experimental (‘Expr.’) JV characteristics of room-temperature-cast (‘As cast’) and hot-cast methods and corresponding simulation (‘Sim.’) results. The hot-cast method shows a current density with a larger magnitude and higher fill factor (area below the JV curve). b, Integrated recombination inside three layers of a solar cell. Peak recombination shifts toward the PCBM/perovskite interface because the barrier for generated carriers is less in the hot-cast case than in the room-temperature-cast case. c, d, Energy band diagram of hot-cast (c) and room-temperature-cast (d) methods. Generated carriers face a lower barrier in the hot-cast case, especially close to the PEDOT/perovskite interface. EC, conduction band; EV, valence band; EFN, electron quasi-Fermi level; EFP, hole quasi-Fermi level.

  9. Extended Data Figure 9: Heat stress tests. (159 KB)

    a, b, Spectra of 2D (a) and 3D (b) perovskite thin films under 80 °C in darkness after the lengths of time indicated (spectra are offset for clarity; ‘ref.’ refers to freshly made thin film, measured after 0 h of heat stressing). c, Ratio of the PbI2 (2θ = 12.7°) and perovskite (2θ = 14.2°) main peaks in the spectra in a and b for the two perovskite materials (2D, blue; 3D, red) over 30 h of heating at 80 °C.

Supplementary information

PDF files

  1. Supplementary Information (401 KB)

    This file contains a Supplementary Discussion, Supplementary Tables 1-4 and Supplementary References.

Additional data