Perovskites-based Solar Cells The challenge of material choice for p-i-n perovskites thin-Film PV Akinola Oyedele
Dec 01, 2014
Perovskites-based Solar Cells
The challenge of material choice for p-i-n perovskites thin-Film PV
Akinola Oyedele
Outline
• Introduction• Background of Perovskites• Evolution of Perovskites• The p-i-n Perovskite Structure• Factors to Consider in Material Choice• Selected Materials• Design Consideration • Conclusion
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Image credit: www.gatescambridge.org
Introduction-Why Solar?
Sun
HydroFossil
WindTidal
Bio-fuels
PV
Solar-Current State-of-the-Art Tech.
Image Credit: NREL, 2014
Solar-Current State-of-the-Art Tech.
Image Credit: Ossila
Solar-Current State-of-the-Art Tech.
Image Credit: G. Conibeer, 2007 Third-generation photovoltaics Material Today 10 11 44 50
Perovskite crystal
The Perovskite Material
• What is Perovskite? • Basic Structure• Other applications• The organometal halide perovskite
http://en.wikipedia.org/wiki/Lev_Perovski
Lev Perovski
(Bisquert, 2013) (Kim, Im, & Park, 2014)
Perovskite crystal
The Perovskite Material
Peng Gao Energy Environ. Sci., 2014, 7,2448
Structural Properties
• Highly crystalline structure (depends on mixed halide, annealing, processing)
• Size of crystallite• Crystallographic changes with temperature
C. W. Chen, Adv. Mater. 2014, 26, 6647–6652 C. W. Chen, Adv. Mater. 2014, 26, 6647–6652
Optical Properties
• High absorption coefficient• Optical absorption as a function of the metal halide • Band- tuning
M. A. Green, Nature Photonics 8, 50-514 (2014) Peng Gao Energy Environ. Sci., 2014, 7,2448
Electronic Properties
• Large Bohr radius Wannier-type excitons• Low binding energies• High dielectric constant • Allow for Charge accumulation • Ambivalent charge transport• Very high e- h+ diffusion lengths
𝐶=𝑘𝜀0 𝜀𝑟 𝐴
𝑑Image Credit: solarwiki.ucdavis.edu
Evolution of Perovskite Solar Cells
A. Hagfeldt, Chem. Rev. 2010, 110, 6595–6663
(Snaith H. J., 2013)
Dye-Sensitized Solar Cell
Achieving ɳ > 20% for Planar p-i-n Perovskites• Improve homogeneity • Narrow band-gap • Multijunction and tandem cells• Better materials for p & n layer to increase FF
Solar Spectrum
Image Credit: www.geog.ucsb.edu
TiOx
PEDOT:PSS
FTO
Perovskite
[60]PCBM
Aluminium
SEM ImageP. Decampo, Nature Comm 4, 2761 (2013)
The P-I-N Device Structure
pi
n
Image Credit: Foozieh Sohrabi
Material Choice (1) - Transporters
• Charge carrier selectivity • Matching of energy levels• Degree of chemical interaction• Conductivity• Light absorption
Materials Choice (2) - Contacts
• Light absorption• Work function • Chemical contamination
Back Contact Electrode:
Gold; work function -5.1 eV
Silver; work function -4.26 eV
Aluminum; work function - 4.28 eV
Transparent Conductive Front Contact:
Fluorine-doped tin oxide (FTO); work function: -4.4 eV (Abrusci,
Stranks, Docampo, Yip, Jen, & Snaith, 2013)
Indium tin oxide (ITO); work function: -4.8 eV (Seo, et al., 2014)
Design Consideration
A B C
Component ThicknessArchitecture A Architecture B Architecture C
Glass
700 nm-900 nm
Glass
700 nm-900 nm
Glass
700 nm-900 nm
ITO
550-700 nm
FTO
700 nm
FTO
700 nm
PTAA
60-70 nm
TiO2
50-90 nm
PC61BM
30-50 nm
CH3NH3PbI3-xClx
350-450 nm
CH3NH3PbI3:
250-300 nm
CH3NH3PbI3-xClx
350-450 nm
TiO2
50-90 nm
Spiro-MeOTAD
150-200 nm
Spiro-MeOTAD
150-200 nm
Ag
60 nm
Au
60 nm
Au
60 nm
Total Thickness
1.77- 2.27 μm
Total Thickness
1.91 - 2.25 μm
Total Thickness
1.99 - 2.36μm
Deposition Methods
One-StepSequential Deposition
Dual-Source Vapor Deposition
Vapor-Assisted Solution Process
Peng Gao Energy Environ. Sci., 2014, 7,2448
Conclusion
• Perovskite absorber: polycrystalline, higher abs coeff., & higher carrier LD
• Efficiency of > 20% can be achieved• There is a bright future for perovskites p-i-n solar cells if the problems
relating to stability and toxicity can be addressed • Proposed configurations guarantee better interface layer engineering
and charge transport.
H. Zhou, Science, 345, 542(2014)
Questions
Selected References
• Boix, P. P., Nonomura, K., Mathews, N., & Mhaisalkar, S. G. (2014). Current progress and future perspectives for organic/inorganic perovskite solar cells. Materials Today , 17 (1), 16–23.
• Edri, E., Kirmayer, S., Mukhopadhyay, S., Gartsman, K., Hodes, G., & Cahen, D. (2014). Elucidating the charge carrier separation and working mechanism of CH3NH3PbI3−xClx perovskite solar cells. Nature Communications , 5, 1-8.
• Liu, M., Johnston, M. B., & Snaith, H. J. (2013). Efficient planar heterojunction perovskite solar cells by vapour deposition. Nature , 501, 395.
• Snaith, H. J. (2013). Perovskites: The Emergence of a New Era for Low-Cost, High-Efficiency Solar Cells. Journal of Physical Chemistry Letters (4), 3623-3630.
• Sum, T. C., & Mathews, N. (2014). Advancements in perovskite solar cells: photophysics behind photovoltaics. The Royal Society of Chemistry .
• Tanaka, K., Takahashia, T., Takuma, B., & Kondoa, T. (2003). Comparative study on the excitons in lead-halide-based perovskite-type crystals CH3NH3PbBr3 CH3NH3PbI3. Solid State Communications , 127, 619-623
• Xing, G., Mathews, N., Sun, S., Lim, S. S., Lam, Y. M., Grätzel, M., et al. (2013). Long-range balanced electron- and hole- transport lengths in organic-inorganic CH3NH3PbI3. Science , 342, 344-347
• Yamamuro, N. O., Matsuo, T., & Suga, H. (1992). Dielectric study of CH3NH3PbX3 (X = Cl, Br, I). Journal of Physics and Chemistry of Solids , 53 (7), 935-939.