Presentation - National High Magnetic Field Laboratory

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Dec 14, 2013 (3 years and 8 months ago)

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An Investigation of the
Applicability of TES
-
Pentacene
in Photovoltaic Devices



David Lehr

Mechanisms of Photovoltaics

Materials

N

type or N
-
doped

Energy allows electrons
to escape the pull of a
nucleus and move freely
through the material.

P
-
type or P
-
doped

Energy causes a bound
electron to bind to another
site leaving a hole behind.
Electrons move in a
“domino effect” filling
holes.

hv

hv

Junction


Light excites carriers
in n and p regions


Charges rush together
at the junction creating
a charge buildup that
acts as a barrier


E field results and
pushes charge
backwards, potentially
powering a circuit



+ + + + + + + + + + + + +


N

P



-

-

-

-

-

-

-

-

-

-

-


Photo
-
effect in Pentacene

Theory
1

1)
Electrons absorb energy and move
from pentacene backbone into
insulating functional groups.

2)
Functional groups act as traps.

3)
Holes are left behind creating a
conduction channel in the
backbone.

4)
System relaxes and electrons are
released from traps filling holes and
closing conduction channel.

First Cell



It Works!
A little bit

Barrier Trouble


Because of the difference in work function
at the pentacene/ITO interface, there is a
potential energy barrier.


Buffer layer may help more carriers cross
the barrier
2
.

Second Type of Cell



It Works
A little better

IV Characteristics



Heating Tricks
3

Conclusions


Pentacene doesn’t seem ideal for
photovoltaics, but it does work on a small
scale.


The charge of the carriers in pentacene
photo
-
effect may not be as hypothesized.


Acknowledgements


This research was supported by the
National Science
Foundation

through the REU program. Many of the
supplies were provided by the
Brooks Condensed Matter
Research group

at the National High Magnetic Field
Laboratory. This research was also made possible by the
Center for Integrating Research and Learning

at the
National High Magnetic Field Laboratory.


Special thanks to Dr. James Brooks, Dr. Jin Gyo Park, and
Ms. Stacy Vanderlaan.



References

[1] J.S. Brooks, T. Tokumoto, E
-
S Choi, D. Graf, N.Biskup, D.L. Eaton.
Persistent photo
-
excited conducting states in functionalized Pentacene.
J. Appl. Phys. In Press.

[2] I. Yoo, M. Lee, C. Lee, D
-
W. Kim, I.S. Moon, D
-
H. Hwang. The
effect of a buffer layer on the photovoltaic properties of solar cells
with P3OT: Fullerene Composites. ICSM 2004 Wollongong Aust. To
be Published.

[3] V. Dyakonov, J. Parisi, D. Chirvase, I. Riedel. Realisation of polymer
-
fullerene solar cells with low recombination losses. ICSM 2004
Wollongong Aust. To be Published.