Presentation on theme: "5/5/2015 GREEN BIO SOLAR CELL. THE SOLAR CHALLENGE With a projected global population of 12 billion by 2050 coupled with moderate economic growth, the."— Presentation transcript:
5/5/2015 GREEN BIO SOLAR CELL
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 CO 2 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.
Solar cells Large sized buildings-Silicon Portable electronics and Small-medium sized buildings Dye sensitized solar cells
Solar Cell Metal complex in PSI and PSII harvest light Fuel Cell Metal complex in PSI and PSII catalyze water splitting to generate electrons Mimicking Plant system -In terms of Activity & Structure for Energy devices Efficient harvesting, synergistic performance, combined activity Efficient transfer
Integration of biological macromolecules with nanostructured organic and inorganic materials Structure-Function Relationship Investigation MATERIALS SYNTHESIS, Extraction Organic Inorganic Biomolecules Nanostructure Materials & Development Solar Cell Organic/QDs Solar Cell Fuel Cell Sensor Device TestingInterface Engineering Organic/Organic MetalOxide /Organic Inorganic / Organic Nano Interfaces Inorganic/ bio metaloxide/bio Bio- Solar Cell Bio- Fuel Cell Bio- Sensor Bio-nano Interface
Evolution of Solar devices Solar cells silicon Polycrystalline (CuInS 2, CuInGaSe 2, CuInSe 2 ) Dye sensitized solar cell, Quantum dot sensitized solar cell II-VI compounds CdTe III-V compounds GaA, InP Cells that generate free electron – hole pair Cells that generate bound electron-hole pair Organic solar cell Polymer solar cell Hybrid solar cells I II III Bio solar cell ? IV Artificial photosynthesis Bio-involved system Our area of research Combination of biological and inorganic (metal oxide) components to create solar cell
Three important components in the current generation of solar cells Cost Size Efficiency Electrolyte Photoelectrode Sensitizer
Structural importance and Mechanism of Natural molecules Proton coupled electron transfer Mechanism in Chemical Dye (DSSCs) 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. 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.
Bio-sensitized Solar Cell (BSSC) Seeram Ramakrishna, V. Renugopalakrishnan Semiconductor Sensitizer Electrolyte Biomolecules Renugopalakrishnan., et al. submitted to Nature nano
Biomolecules as sensitizers Biomolecules Simple molecules Macromolecules Proteins Bacteriorhodospin Tea catechins (fruit extracts ). Cyanin 3-glycoside Chlorophyll a Carotenoids World climate & Energy Event. 1-5 December 2003. Rio de Janerio, Brazil JChemEd.chem.wisc.edu. Vol 75 No.6 June 1998 Chemical Physics Letters 439(2007) 115-120 PNAS | April 4, 2006 | vol 103 | no 14 | 5251-5255 J.Phys.Chem. B, Vol. 109. No.2,2005 J.Phy. Chem. 1993, 97, 6272-6277 Photosystem I & II
Structure of Biomolecules
Overall Design Diagram of BSSC
bR as a potential sensitizer 2 s 70 s 2 ms 0.5 ms 500 fs 8-10 ms ECEC CP L 55 0 N 55 0 M 4 12 O 64 0 H + in H + out Photoisomerized to 13-cis a 9-cis pathway 4-5 potonated all-trans Retinal Quantum Efficiency in methanol -15. 0% Retinal Quantum Efficiency in BR – 67. 0 -64.0% De- and reprotonated Schiff base
Postulated Mechanism of bR in Solar cell PROTON coupled Electron transfer 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
Binding of bR to TiO 2 and ZnO TiO 2 anatase, 1 0 0 IEP = 6.0 ZnO, 0 0 1 IEP = 9.5
Role of Cl - ions in bR triple mutant MD, 1 ns MD, 4 ns MD, 0 ns
Importance of Femtosecond electron injection 2 s 70 s 2 ms 0.5 ms 500 fs 8-10 ms ECEC CP L550L550 N 55 0 M 41 2 b O 64 0 H + in H + out Photoisomerized to 13-cis a 9-cis pathway 4-5 Protonated all-trans Retinal Quantum Efficiency in methanol 15.0% Retinal Quantum Efficiency in BR 67.0-64.0 % De- and reprotonated Schiff base Norbert Hampp, Chem Rev., Vol. 100, 1755-1776, 2000. Norbert Hampp, et al., J. Phys. Chem B., Vol. 106, 13352-13361, 2002.
Construction of band diagram bR-TiO2 system -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 0.0 eV HOMO LUMO 3.78 eV TiO 2 3.2 eV 1.6 eV -5.4 -3.8 bR ? -4.0 Triple Mutant bR e-e- e-e- HOMO Mismatching solar spectrum Low band gap materials preferred to harvest more solar energy 1.2 eV IR-52% Vis-36% UV-12% +e-e-+
Absorption spectra of Ru dyes, PS I and bR
Possible modes of orientation of bR Tatke, Renugopalakrishnan, Prabhakaran, Nanotech. 115, S684-S690,3004 2004.
Computational study – Dipole moment 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. 265 D 125 D
Comparison of 3 Glu bR with Wild type at AM 1.5 We notice that 3 Glu bR is quite responsive
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
Effect of ZnO and TiO2 on the efficiency of biosensitized solar cell Binding of anodes and biomolecules is associated with surface charges and pH. IEP of TiO 2 and ZnO are reported to be 6 and 9.5 respectively, [i] whereas the bacteriorhodopsin (bR), has ca. 4.5. [ii] [i] [ii] ZnO may be the suitable candidate for the immobilization of low IEP proteins [i] [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] [ii]. Hartley, P., Matsumoto, M. & Mulvaney, P. Determination of the Surface Potential of Two- Dimensional Crystals of Bacteriorhodopsin by AFM. Langmuir 14, 5203-5209 ( 1998). ZnO TiO 2 Control control Eff = 0.0 TiO2-bR Eff = 0.02% Isc = 0.09mA/cm2 ZnO-bR Eff = 0.03% Isc = 0.056mA/cm2 Solar=40mW/cm 2 Area= 0.5 cm 2
Biosolar Cells TiO2 + electrolyte (no sensitizer- control) = 0.0 TiO2-bR ~ 0.02% J sc ~ 0.1 mA/cm 2 V OC ~ 0.6V ZnO-bR ~ 0.03% J SC ~ 0.06 mA/cm2 V OC ~ 0.4V Solar intensity=40 mW/cm 2 Cell area= 0.5 cm 2 The first prototype of protein- (bacteriorhodopsin) interface with TiO 2 solar cell has been demonstrated!
TiO2 film electrode solar cell produced a short-circuit photocurrent density (JSC) of 0.038 mA/cm2 whereas wild type bR adsorbed 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 and 3Glu bR respond to the light illumination, however, the triple mutant (3Glu) showed up better photoelectric performance (JSC of 0.038 mA/cm2) compared to wild type bR (0.0269 mA/cm2), which is likely due to more efficiently assembling and binding nature of the mutated protein (3Glu) to the TiO2
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 excitons Another 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.
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.