Biohybrid Solid State Solar CellsDavid R. Needell1,2, Gabriel LeBlanc2, Evan A. Gizzie2, Kane Jennings3, David E. Cliffel2

Department of Physics and Astronomy1, Bowdoin College, ME 04011Departments of Chemistry2 and Chemical and Bimolecular Engineering3, Vanderbilt University, Nashville, TN 37235

Introduction

Materials and Methods

Background!!

➡ Current Photovoltaic Solar Cells’ primary limitation is their extremely high cost to efficiency ratio.!

➡ Photosystem I (PSI) is a protein found in the chloroplast organelle in plants - a crucial part of photosynthesis.!

➡ PSI can excite free electrons under illumination - with nearly perfect quantum efficiency !

➡ PSI can be isolated inexpensively and efficiently[1].!➡ Current state of the art PSI biohybrid solar cells have been “wet"

or liquid cells, i.e. cells with a mediator solution[2].!!Problems!

!➡ Liquid cells can have temperature stability problems, the

solution contains Volatile Organic Compounds (VOC’s), and the mediator often expires quickly - needing replacement.!

!!!!!

!!

Objective!!!

➡ To develop a novel Solid State PSI Solar Cell.

Figure 1: simplified diagram of a liquid PSI solar cell.

Solid State Design

Figure 2: !a conceptual model of the Biohybrid Solid State Solar Cell[4]

Materials and Construction➡ The design requires transparent and flexible electrodes to allow

for PSI illumination and to make electrical contact, respectively.!➡ Two types of electrodes were made using the spin coating

process shown in Figure 3:!1.Reduced Graphene Oxide (rGO)[3]!2.60% Poly(3,4-ethylenedioxythiophene) (PEDOT) in 1-

proponal

Figure 3: !the spin coating process

Conclusions

Future Work

Acknowledgements and References

➡ Both the Silicon-PSI-rGO and the Silicon-PSI-PEDOT Solid State cell generated electrical power.!

➡ The rGO outperformed the PEDOT cell with this design.!➡ PSI remained active when paired with rGO and PEDOT.

This research was made possible by the support of the:!!➡ National Science Foundation (DMR 0907619 and DMR 1263182)!➡ NSF EPSCoR (EPS1004083)!➡ United States Department of Agriculture (2013-67021-21029 USDA) !➡ U.S. Environmental ProtectionAgency (SU8360221) !➡ Scialog Program from the Research Corporation for Science

Advancement

Acknowledgements

References

Multilayered Devices

Flexible Organic Solar Cells

Figure 12: Proposed Multilayered Solid State

PSI Solar Cell - using more advanced protein

alignment techniques.

Figure 13: Flexible Solid State PSI Solar Cell - using

rGO as the working electrode and PEDOT as

the counter.

[1] Ciesielski, P. N. et al. Adv. Funct. Mater. 2010, 20, 4048-4054.![2] Chen, G. et al. J. Electrochem. Soc. 2013, 160, H315-H320.![3] Darby, E. et al. Langmuir. 2014.![4] LeBlanc, G. et al. Adv. Mater. 2012, 24:44, 5959–5962.

Results

rGO Analysis

Biohybrid Solid State Solar Cell Analysis

0 20 40 60-0.05

0.00

0.05

0.10

0.15

0.20

Time (s)

Pho

tocu

rren

t Den

sity

(µA

/cm

2 )

Light On

Figure 7: Characteristic IV curve of a Silicon-PSI-rGO Solar Cell.

Figure 8: Photoresponse of the same Silicon-PSI-rGO Solar Cell.

400 600 8000.0

0.5

1.0

Wavelength (nm)A

bsor

banc

e

1 mg/ml RGO2 mg/ml RGO3 mg/ml RGO4 mg/ml RGO5 mg/ml RGO

0

10

20

30

Thic

knes

s (n

m)

Figure 4: UV-VIS Photospectroscopic analysis of rGO in order to determine how much light can pass through to the PSI.

Figure 5: Thickness of the rGO film with respect to the concentration of the

solution.

Figure 6: Resistivity of various rGO films.

400 600 8000.0

0.5

1.0

Wavelength (nm)

Abs

orba

nce

1 mg/ml RGO2 mg/ml RGO3 mg/ml RGO4 mg/ml RGO5 mg/ml RGO

Legend

Purpose: to optimize transparency and conductivity in rGO samples.

Conclusion: 2 mg/ml rGO works best as our counter electrode given its resistivity and transparence.

Purpose: to determine if a Silicon-PSI-rGO !Solar Cell generates electricity.

Purpose: to determine if a Silicon-PSI-PEDOT! Solar Cell generates electricity.

Figure 9: Characteristic IV curve of a Silicon-PSI-

PEDOT Solar Cell.

Figure 10: Photoresponse of the same Silicon-PSI-

PEDOT Solar Cell.

0 50 100

-0.04

-0.02

0.00

0.02

Voltage (mV)

Cur

rent

Den

sity

(µA

/cm

2 )

Light On Jsc = 0.017 µA/cm2

Voc = 35.3 mVFF = 0.31Pmax = 180 pW/cm2

Light Off

0 50 100

-0.04

-0.02

0.00

0.02

Voltage (mV)

Cur

rent

Den

sity

(µA

/cm

2 )

Light OnLight Off

Jsc = 0.009 µA/cm2

Voc = 45.5 mVFF = 0.30Pmax = 116 pW/cm2

0 20 40 60-0.01

0.00

0.01

0.02

0.03

0.04

Time (s)

Ph

oto

curr

ent D

ensi

ty (µ

A/c

m2 )

Light On

0.0001

0.001

0.01

0.1

1

Res

istiv

ity (Ω

⋅m)

Figure 11: Energy band diagrams of both cells.