Transcript Slide 1
Dye-Sensitized Solar Cells Sonja A. Francis 7th March 2012 Solar Irradiation Solar irradiation is the amount of radiant energy emitted by the sun per area and unit time for a given wavelength of light. Visible IR M. Skompska. Synthetic Metals 2010, 160, 1-15. 2 Is Solar Energy Viable? Potential amount of solar energy collected annually in Alberta with a 1 kW capacity solar cell system 3.96 – 5.04 GJ Photovoltaic potential GJ per 1kW capacity solar cell Residential Electrical Energy Usage in Alberta (2009) > 32,000,000 GJ Maximum solar system capacity required ~ 8,300,000 kW 8.3 MW J. Bell, T. Weis, Greening the grid, Powering Alberta’s future with renewable energy. 2009 http://pubs.pembina.org/reports/greeningthegrid-report.pdf. Retrieved 18th March 2010. 3 General Solar Cell Structure h Negative Terminal Positive Terminal Cell structure Load Electron flow in external circuit T. Markvart, L.Castañer. “Principles of Solar Cell Operation” in Practical Handbook of Photovoltaics Fundamentals and Applications, 2003, Elsevier, Oxford, UK. 4 Types of Solar Cells • Semiconductor solar cell • Thin film solar cell – E.g. Crystalline silicon – E.g. CdS/CdTe • Organic/Polymer solar cell – E.g. Fullerene/Poly-(p-phenylvinylene) n V. Fthenakis. Renewable Sustainable Energy Rev. 2009, 13, 2746 - 2750. Y. Cao et al. Sol. Energy Mat. Sol Cells 2010, 94, 114 - 127. M.A. Green, K. Emery, Y. Hishikawa, W. Warta, Prog. Photovolt.: Res. Appl. 2009, 17, 320 - 326. 5 Dye-Sensitized Solar Cells (DSSCs) • Main components www.chemphys.lu.se/research/subjects/cells/ Retrieved 16th March 2010 – Semiconductor electrode – Dye sensitizer – Redox couple in an electrolyte – Transparent counter electrode coated with a catalyst V. Fthenakis. Renewable Sustainable Energy Rev. 2009, 13, 2746 - 2750. Y. Cao et al. Sol. Energy Mat. Sol Cells 2010, 94, 114 - 127. 6 Semiconductor • E.g. Semiconductor oxides SEM – ZnO, SnO2, Nb2O5, In2O3 • TiO2 (anatase) – High porosity (60%) – High stability – Wide band gap energy 3.2 eV ( 388 nm) S. Mori, S. Yamigada, “TiO2-based Dye-Sensitized Solar Cell” in Nanostructure Materials for Solar Energy Conversion, T. Soga (Ed.), 2006, Elsevier. M. Grätzel. Acc. Chem. Res. 2009, 42, 1788 - 1798. 7 Sensitizer Dye Suitable dyes absorb strongly in the visible region. (in DMF) N ε (mmol/cm2) N Zn N 15000 N COO NBu4 HOOC HO2C N N 10000 N Ru N NCS NCS HO2C 5000 COOH COO (in EtOH) NCS NBu4 SCN NCS Ru N HO2C 0 400 600 800 l (nm) N 1000 N CO2H (in EtOH) CO2H D. L. Officer et al. J. Phys. Chem. C, 2007, 111, 11760–11762. H. Sugihara et al. Sol. Energy Mat. Sol. Cells 2010, 94, 297 – 302. 8 Sensitizer Dye Suitable dyes chemisorb to the semiconductor. E.g. One molecule of N719 exhibiting bidentate binding to TiO2. surface TiO2 surface OH OH Ti Ti Y. Narita et al. Electrochem. Solid-State Lett. 2009, 12, B167 – B170. 9 Redox couple/Electrolyte Iodide/Triiodide I3- + 2e- 3I- h 3 I- Dye Counter electrode Semiconductor Electron transfer Electron transfer Electron transfer Dye + I3Electron flow External Circuit B. C. O’Regan, J. R. Durrant, Acc. Chem. Res. 2009, 42, 1799 – 1808. 10 Counter Electrode E.g. Platinum loaded on Fluorine-doped SnO2 (FTO) – a transparent conducting oxide (TCO) Pt is an excellent catalyst for triiodide reduction x Rare and expensive x Incompatible with some electrolytes e.g. poly sulfide I32 e- To external circuit 3II3-/I- Pt FTO G. Boschloo; A. Hagfeldt. Acc. Chem. Res. 2009, 42, 1819 – 1826. 11 Processes in the DSSC 1. Photo-excitation D* hυ Ox D/D+ Red 2. Electron injection and dye-relaxation 3. Electron flow 4. Re-entry 5. Reduction of electrolyte Semiconductor Dye Electrolyte CE 6. Dye regeneration (reduction) B. C. O’Regan, J. R. Durrant, Acc. Chem. Res. 2009, 42, 1799 – 1808. 12 Electron transfer in the DSSC VOCISC – open circuit voltage; maximum voltage - short circuit current; maximum current the dye-sensitized solar(no cellload). can achieve. achieved Conduction Band LUMO Potential/V Fermi Level VOC Redox Potential Fermi Level HOMO Semiconductor Dye Molecule Electrolyte Cathode not drawn to scale G. Boschloo; A. Hagfeldt. Acc. Chem. Res. 2009, 42, 1819 – 1826. 13 Electrical Losses in DSSCs D* 1. Dye relaxation 2. Recapture by oxidised Red Ox electrolyte D+/D Semiconductor Dye Electrolyte 3. Recapture by Pt oxidised dye A. J. Bard; L. R. Faulkner. “Photoelectrochemistry and Electrogenerated Chemiluminescence” in Electrochemical Methods Fundamentals and Applications, 2nd Ed. 2001, Wiley, New Jersey, USA. 14 Most Efficient DSSC (11.1%) J-V and Power curves JSC 20.9 mA/cm2 VOC 0.736 V • Incident radiation 100 mW/cm2 • TiO2 semiconductor • Dye sensitizer NCS SCN NCS Ru N HO2C N N CO2H CO2H • I- /I3- in ionic liquid electrolyte L. Han. et al. J. Jpn. Appl. Phys. 2006, 45, L638 – L640. 15 Make your own solar cell at home http://www.youtube.com/watch?v=bVwzJEhM mD8&feature=player_embedded http://www.wired.co.uk/magazine/archive/201 0/03/how-to/how-to-make-your-own-solarcell- Retrieved 8th March 2012 16 Current Products Sony’s functional Hana-Akari DSSC lanterns. G24 Innovations Back pack DSSC 0.5W under direct sunlight. Claims 12 % efficiency. P. Patel “Dye-Sensitized Solar to Go” in Technology Review October 2009, MIT Publications. Retrieved 18th March 2010 Sony design. http://www.sony.net/Fun/design/activity/sustainable/dssc.html. Retrieved 18th March 17 2010. Additional References http://www.itechnews.net /tag/solar-panel/ Retrieved 16th March 2010 http://solarpanelspower.net /solar-panels/miniature-pv-cells Retrieved 16th March 2010 NRC PV Potential Interactive map, glfc.cfsnet.nfis.org/mapserver/pv/index.php?lang=e. Retrieved 18th March 2010. Electricity Statistics. http://www.energy.alberta.ca/Electricity/682.asp. Retrieved 18th March 2010. http://www.ecf.utoronto.ca /~luzheng/research.html Retrieved 16th March 2010 18