Polymer Crystallization on Curved Surfaces

Steve Kuei

Overview

• Introduction– Organic electronics– Motivation

• Experimental– Previous work– Buckling Structures– Atomic Force Microscopy

• Conclusions• Future work

AlAl

Organic Electronics

• Solar Cells

ITOITO

Motivation

• Polymer crystallization

Previous work

A. Hexemer, V. Vitelli, E.J. Kramer, G. H. Fredrickson

Previous work

A. Hexemer, V. Vitelli, E.J. Kramer, G. H. Fredrickson

Curvature

• Principal curvatures,

• Mean curvature – average of principal curvatures

• Gaussian Curvature – product of principal curvatures

Buckling Structures

Atomic Force Microscopy

Wikipedia, by Askewmind Images by Vijay Narayan

AFM and buckling structures

AFM and buckling structures

P3EHT

Polymer synthesized by Segalman Group, Berkeley

M.W. 7k g/mol

P3EHT – spin coated

P3EHT – annealed for 12 hours

P3EHT – annealed for 12 hours

P3EHT – annealed for 2 days

Future work

• Film thickness– Currently too thick, pooling in trenches– Orientation underneath surface layer is unknown

• Buckling structures– Need to optimize amplitude and period of buckling

structures so that polymer stays on the peaks– Need to control buckling structures to have regularly

occurring gaussian curvature

• Conclusions– Gaussian curvature appears to dominate, especially

after annealing for longer periods of time, aligning polymer fibers along the troughs.

Acknowledgements

• Princeton Environmental Institute Energy Grand Challenge

• MIRTHE/PCCM REU program

• Professor Loo, Professor Yao, Dr. Hexemer• Eleni Pavlopoulou, Jongbok Kim, Stephanie Lee,

Pilnam Kim, Rich Fiorillo, Atray Dixit, Vijay Narayan