04/21/23

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 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.

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 ofActivity & Structure for Energy devices

Efficient harvesting, synergistic performance, combined activity

Efficient transfer

Integration of biological macromolecules with nanostructuredorganic and inorganic materials

Structure-Function Relationship Investigation

MATERIALS SYNTHESIS, Extraction

OrganicInorganicBiomolecules

Nanostructure

Materials & Development

Solar CellOrganic/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(CuInS2, CuInGaSe2, CuInSe2)

Dye sensitized solar cell, Quantum dot sensitized solar cell

II-VI compoundsCdTeIII-V compoundsGaA, InP

Cells that generate free electron – hole pair

Cells that generate bound electron-hole pair

Organic solar cellPolymer 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

SemiconductorSensitizer

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 fs8-10 ms

EC

CP

L

55

0

N55

0

M4

12 M412

O64

0

H+in H+

out

Photoisomerized to 13-cis

a 9-cis pathway4-5

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 TiO2 and ZnO

TiO2 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 nsMD, 0 ns

Importance of Femtosecond electron injection

2 s

70 s

2 ms

0.5 ms

500 fs8-10 ms

EC

CP

L5

50

N55

0

M41

2 b

O64

0

H+in H+

out

Photoisomerized to

13-cisa 9-cis pathway4-5

Protonated all-trans

Retinal Quantum Efficiency in methanol15.0%

Retinal Quantum Efficiency in BR67.0-64.0%

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

-1.0

0.0

eV

HOMO

LUMO

3.78 eV

TiO2

3.2 eV

1.6 eV

-5.4

-3.8

bR

?

-4.0

Triple Mutant bR

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-+

2500

2000

1500

1000

500

0Pho

toem

issi

on in

tens

ity (ar

b. u

nits

)

2520151050

binding energy (eV)

Ip25J y07021 protein Ip25J y07023 TiO2 Ip25J y07025 ITO

4.0 eV

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

-0.1

-0.05

0

0.05

0.1

0 0.2 0.4 0.6 0.8 1

Voltage (V)

Cu

rre

nt

(mA

/cm

2)

Light Shine_3Mutant Light Shine_wildType

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/cm2Cell Area: 1 cm2Electrolyte: LiI/KCl in Distilled water

-0.100

-0.080

-0.060

-0.040

-0.020

0.000

0.020

0.040

0.060

0.080

0.100

0 0.2 0.4 0.6 0.8 1 1.2

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 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. Langmuir 14, 5203-5209 (1998).

ZnO

ZnOTiO2Control

-0.15

-0.05

0.05

0.15

0 0.2 0.4 0.6 0.8Voltage (V)

Cu

rre

nt

(mA

/cm

2)

control

Eff = 0.0

TiO2-bR

Eff = 0.02%

Isc = 0.09mA/cm2

ZnO-bREff = 0.03%Isc = 0.056mA/cm2

Solar=40mW/cm2

Area= 0.5 cm2

Biosolar Cells

-0.01

0.09

0 0.2 0.4 0.6 0.8Voltage (V)

Cu

rre

nt

(mA

/cm

2)

TiO2 + electrolyte (no sensitizer-control)

= 0.0

TiO2-bR ~ 0.02%Jsc ~ 0.1 mA/cm2

VOC ~ 0.6V

ZnO-bR ~ 0.03%JSC ~ 0.06 mA/cm2VOC ~ 0.4V

Solar intensity=40 mW/cm2

Cell area= 0.5 cm2

The first prototype of protein- (bacteriorhodopsin) interface with TiO2 solar cell has been demonstrated!

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

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.

Thermal motion of bR in the membrane