Crystallization of Small Molecules for Organic Electronic

ApplicationsJessica Lynn Saylors, Anna Hiszpanski, and Yueh-Lin (Lynn)

Loo

07 October 2011Summer of Learning Symposium 2011

Why organic electronics?

• Mechanically Flexible

• Large Area

• Chemical Versatility

www.plasticlogic.com

Transistors – Building Blocks of Organic Electronics

organic semiconductor

gate + dielectric

source

drain

How an Transistor works

S D

Organic

Insulator

Gate electrode

0 V 0 V 0 V -1 V 0 V -5 V

0 V -5 V -5 V

- - - - - - - - -+ + + + + + + + +- - - - - - - - -+ + + + + + + + + + + + + + ++ +

- - - - - - - - -+ + + + + + + + +- - - - - -

Cut-off regime

Linear regime Saturation regime

Organic field-effect transistor (OFET)

Xiao, S. et al. Angew. Chem. Int. Ed. 2005.

Contorted Hexabenzocoronene

(HBC)

HBC

Crystallizing HBC Thin Films

π stacking

π-face

HBC

Amorphous HBC

Partially Crystallized HBC

Thermal Evaporation

Thickness Gradient: 15nm – 250nm

HBC Mobility vs. Thickness

46 48 50 52 54 563.03.54.04.55.05.56.06.57.07.5

Mob

ility

*10-4

(cm

2 /Vs)

Estimated Thickness (nm)

Macroscopic Morphology

15nm

33nm

50nm

120nm

Optical Micrographs for Kinetics AnalysisHBC thin film - annealed at 240°C

t = 0.5 min t = 1 min t = 1.5 min

t = 2 min t = 2.5 min t = 3 min

Avrami Kinetics

n: variable that gives some indication

regarding mode of crystallization

K: indication of therate of crystallization

%crystallized

0 20 40 60 80 100 120 140 160 180

0.5

1.0

1.5

2.0

2.5

3.0

3.5

227C 240C 255C

n

Thickness (nm)

Avrami n vs. Thickness

0 20 40 60 80 100 120 140 160 180

0.5

1.0

1.5

2.0

2.5

3.0

3.5

227C 240C 255C

n

Thickness (nm)

Avrami n vs. Thickness

American Institute of Chemical Engineers

http://www.aiche.org/Students/Conferences/national.aspx

http://www.minneapolisconventioncenter.com/

Acknowledgments

• Loo Group– Anna Hiszpanski– Professor Loo

• Princeton Environmental Institute

• Siebel Energy Grand Challenge

http://www.princeton.edu/pei/

Loo Group, March 2011