1 st INTERNATIONAL CONGRESS ISEREE 2013 Quito Ecuador November, 2013 Javier C. Ramirez Perez, Ph.D., P.E. Prometheus Research Professor CIBE-ESPOL Dye-sensitized solar cell using natural dyes from Ecuador
Summary Introduction Dye Sensitized Solar Cell (DSSCs) Limitations de celda PV Basic Structure of a DSSC Substrate (TCO), semiconductor, pigments, Assembly and Characterizacion Material and methods Selected natural pigments from Ecuador To date Results Natural dyes process extraction and characterization Conclusion and recommendations
Introduction Growing Energy and Environmental Concerns Fossil fuels depletion Climate change, global warming Attention to alternative energy and/or renewable sources of energy: wind, hydropower, biomass and solar energy RamirezPerez,JC CO2 the major contributor of GHG 3
Photovoltaic Solar Electricity Potential in Ecuador World Solar Irradiation Map solar belt 20 o and 30 o latitute 4 RamirezPerez,JC Source: World Bank, IMF, AT Kasney analysis
Future Energy Consumption 2006 = 13 TW, ( 4.1 *10 20 J/yr) 2050 = estimated 28 TW RamirezPerez,JC 5
tovoltaic Solar Electricity Potential in Ecuador The yearly solar irradiation on horizontal surface in the Equator is 1800-2300 kw m -2 EP=1.367kWm -2 - the solar constant solar radiation power outside the Earth s atmosphere Ramirez Perez, J.C. The fundamental requirement of any solar to electric conversion system is the absorption of a significant part of the incident solar radiation with a consequence utilization of the energy of the photons in an electrical process World matrix energy change is solar energy incident 3*10 24 J/yr, exceeds world consumption today 4 *10 20 J/yr. Solar cells sensitized by natural pigment, Dye-Cells, are promised ways to utilize solar energy for electricity generation on competitive cost-wise with conventional energy http://www.pv.unsw.edu.au/am1.5.html 6
Photovoltaic Cells Developments RamirezPerez,JC DSSC DSSC 7
PV cells limitations Low efficiency Very expensive Silicon Efficiency % ZnO + thin layer of n-cds p-cigs = solid solution of Cu(In,Ga)Se 2 (1-3 µm) Mo (back electrode) RamirezPerez,JC 8 Substrate (glass) RamirezPerez,JC
Dye-sensitized Solar Cells (DSSCs) RamirezPerez,JC 9
Basic Structure and Components of DSSC Schematic of the energy flow in a DSSC* 10 RamirezPerez,JC *Tobin et al., 2011 Optik,122, 1225-1230
Principle of DSSC Operation A photon energy E=hc/λ. If the E >> the band gap of the semiconductor the photon can be absorbed, an e- is excited from the valence to the conduction band, which allow I 20 μm 10 25 nm 3I - I 3 - + 2e - (anode) I 3 - + 2e - 3I - (cathode) RamirezPerez,JC
Natural Dyes-Pigments The purpose of the dye is to absorb light and inject the photo-exited electrons into the conduction band of the semiconductor and maintain photo stability for long-term use. Ru-centered polypyridyl metal org. complexes have been favored in DSC Strong absorption of visible light Favorable spatial separation of HOMO and LUMO (rapid e-/ injection) Repetitively Oxidized/Red without degradation Drawnbacks Environmental and economical costs Ru is a rare metal, a resource limited Industrial applicacion Ru-based dyes is costly Toxic and volatile Synthetic organic dyes have been used as effective sintetizers Synthesis, purification procedures make high producction costs RamirezPerez,JC 12
From Organometallic to Natual dyes N3 D5 LUMO N719 HOMO RamirezPerez,JC 13
RamirezPerez,JC Natural Dyes-Sensitizers An economic and environmental alternative to Ru-based dyes and Synthetic organic dyes is natural plant pigments Natural plant pigments have the potential to improve the economic and environmental benefits of DSSCs. To achieve a high light to energy conversion efficiency the properties of the dye adsorbed on the semiconductor particle surface are esential The energy of the exited state of the molecule should be about 1.35 ev above the electronic ground state, the exited state of the absorbed dye molecule should be only slightly above the conduction band edge of the TiO 2 The ground state of the molecule should be only slightly below the redox potential of the electrolyte The adsorbed molecule should be stable enough at the semiconductor electrolyte interface to sustain for several years 14
RamirezPerez,JC Semiconductor TiO 2 The most commonly used wide band gap semiconductor in DSSCs The efficiency depends on the properties of nanostructured TiO 2 photoelectrode used for light absorption and e- transfer Preparation of TiO 2 result in a faster photoresponse and higher e- collection efficiencies. The purpose of electrolyte is to donate electrons to oxidized sensitizer to prevent the excited electrons recaptured by the sensitizer. Transparent material that allows the light to go through and has good conductivity and fast redox reaction. Liquid Iodide/Tri-iodide is the most commonly used electrolyte for DSSC Conducting glas Resistance TiO2 Dye Redox Electrolyte 15
Materials y Methods Experimental Design Figure 2. Overall experimental design RamirezPerez,JC 16
RamirezPerez,JC Results 17
Results Ratio:10 g/250 ml EtOH 95%-HCl 0.1N; ph 1-3, T<40 o C, (d) λ max in the visible range is shown. Natural dye image plant material solvent color ph FD maximu m Abs (nm) λmax (nm) Escancel;Iresin e herbstii Hook Mora; Rubus robustus C. Presl Mortiño; Solanum americanum Mill. Remolacha; Beta vulgaris dried (leaves) dried (fruit) fresh (fruit) dried (fruit) dried (root) (c) dark read 1.13 20 0.47 526 (c) dark read 1.91 40 1.244 511 (b) dark read - 40 1.003 515 (c) dark read 40 0.946 514 (c) dark read 3.21 20 2.03 534 RamirezPerez,JC 18
RamirezPerez,JC Spectrophotometric analysis of natural photopigments
Results A) In acid solution anthocyanine dyes appear red due to an intense band at ca. 520 nm: Mortiño, Mora, Escancel*. B)Absortion spectra on TiO2 film of anthocyanine and flavonoide extracts from ethanolic at 0.1 M aq solution for various pigments* RamirezPerez,JC (*)Giuseppe et al. (2009) Energy Environ. Sci.,20, 1162-1172
Results C) UV-Vis spectrum of raw red turmip extracts in 0.1 M HCl solution showing the betaaxnthin (484 nm) and betanin (536 nm): Remolacha D) Absortion spectra on TiO2 film of betalains from red trunip * To date selected chlorophyll derivatives, anthocyanine and betalain extracts are the most succesful natural sensitizers to nanofabricate DSSCs and maximum conversion efficiencies under simulated sunlight. Mortiño appear as more suitable natural pigment to achieving viable DSSC to generate clean energy RamirezPerez,JC (*)Giuseppe et al. (2009) Energy Environ. Sci.,20, 1162-1172
RamirezPerez,JC Conclusions Nanofabrication de DSSC using mortiño* *Dr. Neyde Y. Murakami I Lab. Fotochemistry and Energy Conversion,Chemestry Institute, Sao Paulo Brazil. In conlusion natural pigments depend on the product used (fruit, leave, stem, seeds). Mortiño extract suggests to be a good sensitizer and good stability for DSSC. Is important continue looking for natural pigments in all biodiversity of flowers and fruits present in Ecuador in order to find appropriate natural pigments for DSSC nanofabricatiom to generate a clean and sustainable energy.
Acknowledgements Prometheus Program of Senescyt-Ecuador Universidad Técnica Particular de Loja (UTPL) Ing. Natali Solano (Coauthor) Centro de Investigaciones Biotecnológicas del Ecuador, CIBE-ESPOL RamirezPerez,JC 23