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3/11/2014

GREEN BIO SOLAR CELL. 3/11/2014. THE SOLAR CHALLENGE. With a projected global population of 12 billion by 2050 coupled with moderate economic growth, the total global energy consumption is estimated to be ~ 28 TW. Current global use is ~ 11 TW.

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3/11/2014

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  1. GREEN BIO SOLAR CELL 3/11/2014

  2. THE SOLAR CHALLENGE With a projected global population of 12 billion by 2050 coupled with moderate economic growth, the total global energy consumption is estimated to be ~28 TW. Current global use is ~11 TW. To cap CO2 at 550 ppm (twice the pre-industrial level), most of this additional energy needs to come from carbon-free sources. Solar energy is the largest non-carbon-based energy source (100,000 TW). However, it has to be converted at reasonably low cost.

  3. Solar cells Large sized buildings-Silicon Dye sensitized solar cells Portable electronics and Small-medium sized buildings

  4. Mimicking Plant system -In terms ofActivity & Structure for Energy devices Fuel Cell Metal complex in PSI and PSII catalyze water splitting to generate electrons Efficient harvesting, synergistic performance, combined activity Solar Cell Metal complex in PSI and PSII harvest light Efficient transfer

  5. Integration of biological macromolecules with nanostructured organic and inorganic materials Nano Interfaces Organic/Organic Solar Cell Organic/QDs Solar Cell Bio- Solar Cell MATERIALS SYNTHESIS, Extraction Organic Inorganic Biomolecules Nanostructure Fuel Cell Inorganic / Organic Inorganic/ bio Bio- Fuel Cell Sensor MetalOxide /Organic Bio- Sensor metaloxide/bio Materials & Development Interface Engineering Device Testing Structure-Function Relationship Investigation Bio-nano Interface

  6. silicon I Cells that generate free electron – hole pair Our area of research Artificial photosynthesis II-VI compounds CdTe III-V compounds GaA, InP Solar cells Bio-involved system II Cells that generate bound electron-hole pair Polycrystalline (CuInS2, CuInGaSe2, CuInSe2) Dye sensitized solar cell, Quantum dot sensitized solar cell Hybrid solar cells III Organic solar cell Polymer solar cell IV Bio solar cell ? Evolution of Solar devices Combination of biological and inorganic (metal oxide) components to create solar cell

  7. Sensitizer Three important components in the current generation of solar cells Efficiency Electrolyte Photoelectrode Cost Size

  8. Structural importance and Mechanism of Natural molecules The key to obtain such rapid electron ransfer is to endow the dye with a suitable anchoring group, such as a carboxylate or phosphonate substituent or a catechol moiety, through which the sensitizer is firmly grafted onto the surface of the Titania. Proton coupled electron transfer Mechanism in Chemical Dye (DSSCs) The surface dipole is generated by proton transfer from the carboxylate groups of the sensitizer to the oxide charging the solid positively and leaving an excess negative charge on the dye.

  9. Biomolecules Bio-sensitized Solar Cell (BSSC)Seeram Ramakrishna, V. Renugopalakrishnan Electrolyte Sensitizer Semiconductor Renugopalakrishnan., et al. submitted to Nature nano

  10. Biomolecules as sensitizers Biomolecules • Macromolecules • Proteins • Bacteriorhodospin Simple molecules • Tea catechins (fruit extracts). • Cyanin 3-glycoside World climate & Energy Event.1-5 December 2003. Rio de Janerio, Brazil PNAS | April 4, 2006 | vol 103 | no 14 | 5251-5255 • Photosystem I & II JChemEd.chem.wisc.edu. Vol 75 No.6 June 1998 • Chlorophyll a J.Phy. Chem. 1993, 97, 6272-6277 • Carotenoids Chemical Physics Letters 439(2007) 115-120 J.Phys.Chem. B, Vol. 109. No.2,2005

  11. Structure of Biomolecules

  12. Overall Design Diagram of BSSC

  13. bR as a potential sensitizer O640 Photoisomerized to 13-cis a 9-cis pathway4-5 500 fs 8-10 ms N550 2 ms Retinal Quantum Efficiency in methanol -15. 0% L550 0.5 ms Retinal Quantum Efficiency in BR – 67. 0 -64.0% 70 ms potonated all-trans 2 ms M412 EC M412 H+in CP H+out De- and reprotonated Schiff base

  14. Postulated Mechanism of bR in Solar cell Photoexcitation of the sensitizer resulted in the changes in protonation state of acidic and basic groups in the protein. They produce a transmembrane potential gradient that causes injection of an electron into the conduction band of the oxide and transport through the metaloxides to the collection electrode. Hence, the principle of bR in solar device is based on bR proton coupled electron transfer upon photoexcitation • PROTON coupled Electron transfer

  15. Binding of bR to TiO2 and ZnO ZnO, 0 0 1 IEP = 9.5 TiO2 anatase, 1 0 0 IEP = 6.0

  16. MD, 1 ns MD, 0 ns MD, 4 ns Role of Cl- ions in bR triple mutant

  17. O640 Photoisomerized to 13-cis a 9-cis pathway4-5 500 fs 8-10 ms N550 2 ms Retinal Quantum Efficiency in methanol 15.0% L550 0.5 ms Retinal Quantum Efficiency in BR 67.0-64.0% 70 ms Protonated all-trans 2 ms M412 EC b H+in CP H+out De- and reprotonated Schiff base Importance of Femtosecond electron injection Norbert Hampp, Chem Rev., Vol. 100, 1755-1776, 2000. Norbert Hampp, et al., J. Phys. Chem B., Vol. 106, 13352-13361, 2002.

  18. IR-52% Vis-36% UV-12% • Mismatching solar spectrum • Low band gap materials preferred to harvest more solar energy 1.2 eV + e-+ e- 0.0 Construction of band diagram bR-TiO2 system -1.0 eV e- -2.0 -3.8 e- -3.0 LUMO ? -4.0 1.6 eV -4.0 3.78 eV HOMO -5.0 Triple Mutant bR 3.2 eV -5.4 -6.0 bR HOMO -7.0 TiO2

  19. Absorption spectra of Ru dyes , PS I and bR

  20. Possible modes of orientation of bR Tatke, Renugopalakrishnan, Prabhakaran, Nanotech. 115, S684-S690,3004 2004.

  21. Computational study – Dipole moment 125 D 265 D The dipole moment vector of bR aligns to the exterior-cytoplasm axis (vertical) upon formation of the physiological trimer. A monomer of bR is shown as ribbons colored from blue (N-terminus) to red (C-terminus) and with its retinal chromophore in purple ball-and-stick representation. The monomer dipole moment vector, which has a magnitude of 265 D, is shown as a grey arrow, while that of the trimer to which this monomer belongs, with a value of 125 D, appears in Sienna brown.

  22. Comparison of 3 Glu bR with Wild type at AM 1.5 We notice that 3 Glu bR is quite responsive

  23. Measurement at high concentration of 3 Glu bR (4mg/ml) at pH 8 Air Mass 1.5 solar spectrum Conversion efficiency: 0.02% Isc: 0.08 mA/cm2 Cell Area: 1 cm2 Electrolyte: LiI/KCl in Distilled water

  24. Effect of ZnO and TiO2 on the efficiency of biosensitized solar cell ZnO-bR Eff = 0.03% Isc = 0.056mA/cm2 TiO2-bR Eff = 0.02% Isc = 0.09mA/cm2 control Eff = 0.0 Solar=40mW/cm2 Area= 0.5 cm2 ZnO Control TiO2 ZnO Binding of anodes and biomolecules is associated with surface charges and pH. IEP of TiO2 and ZnO are reported to be 6 and 9.5 respectively,[i] whereas the bacteriorhodopsin (bR), has ca. 4.5.[ii] ZnO may be the suitable candidate for the immobilization of low IEP proteins [i]. Topoglidis, E., Cass, A. E. G., Regan, B. O. & Durrant. J. R. Immobilisation and bioelectrochemistry of proteins on nanoporous TiO2 and ZnO films. J. Elect. Chem. 517, 20-27 (2001). [ii]. Hartley, P., Matsumoto, M. & Mulvaney, P. Determination of the Surface Potential of Two-Dimensional Crystals of Bacteriorhodopsin by AFM. Langmuir14,5203-5209 (1998).

  25. Biosolar Cells Solar intensity=40 mW/cm2 Cell area= 0.5 cm2 TiO2-bR h ~ 0.02% Jsc ~ 0.1 mA/cm2 VOC ~ 0.6V ZnO-bR h ~ 0.03% JSC ~ 0.06 mA/cm2 VOC ~ 0.4V TiO2 + electrolyte (no sensitizer-control) h = 0.0 The first prototype of protein- (bacteriorhodopsin) interface with TiO2 solar cell has been demonstrated!

  26. TiO2 film electrode solar cell produced a short-circuit photocurrentdensity (JSC) of 0.038 mA/cm2 whereas wild type bRadsorbed TiO2 cell showed only 0.0269 mA/cm2 as JSC.However, for both the type of bR, the open-circuit photovoltage(VOC) was about 0.39 V.The experimental results confirmed that both wt bR and3Glu bR respond to the light illumination, however, thetriple mutant (3Glu) showed up better photoelectric performance(JSC of 0.038 mA/cm2) compared to wild typebR (0.0269 mA/cm2), which is likely due to more efficientlyassembling and binding nature of the mutated protein(3Glu) to the TiO2

  27. Energy Loss in the Various Steps in the Solar Cascade • The Shockley-Queisser limit rests on the assumption that one photon can produce only one electron-hole pair in the presence of a single energy gap. However, this limit can be violated if one photon can lead to multiple electron-hole pairs or excitonsAnother related issue is the effect of a band gap distribution on the cell efficiency. These important problems can be addressed by calculating the electronic structure of the protein chromophore with reliable first principles methods. • The coupling of the excited protein with the substrate causes energy dissipation. In order to optimize the charge transfer efficiency, reliable first principles calculations are needed to simulate the energy losses. • A mathematical theory for the electrolyte phase between the electrodes in the BSSC is another important tool we plan to develop in order to control various energy losses.

  28. An understanding and mastering interactions and charge transfer at the protein-substrate interface Finding a bR mutant that absorbs light in the right part of the spectrum, that enhances charge separation, and that ejects electrons to be captured by wide-gap semiconductors Finding an optimal non-invasive electrolyte for recharging the protein Developing mathematical models to predict ultimate efficiency, allowing for multiple exciton production and intermediate band light-adsorption processes, and practical efficiency, taking into account non-radiative losses in the semiconductor/br/electrolyte microstructure.

  29. Thermal motion of bR in the membrane

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