Crystallization of TES ADT in Constrained Channels Abby Grosskopf, Anna Hailey, Lynn Loo Loo Lab Group: Polymer and Organic Electronics Laboratory Princeton University

Background Information Organic Semiconductor: An organic material with an electrical conductivity Benefits of using organic semiconductors over inorganic semiconductors: Solution-processable Inexpensive to fabricate Suitable for large area processing Thin films comprising organic molecules have promising applications, such as organic thin film transistors, and solar cells. Other than of solution-processing: thermal evaporation Easily tunable- change chemistry of the molecule, very easily http://www.sigmaaldrich.com/technical-documents/articles/material-matters/organic-materials.html http://www.sunnysolarlightgarden.com/solar-yard-lights-work/

Crystallization of TES ADT TES ADT is a solution-processable organic semiconductor. TES ADT undergoes spherulitic growth when spin coated from 2 wt% solution in toluene then exposed to 1,2-dichloroethane vapor. When speaking go through process chronologically as-spun film crystallized film Expose to 1,2-dichloroethane vapor1 Spin-coat from 2 wt% solution in toluene 250 μm Lee, Stephanie. (2012). Processing-Structure- Function Relationships In Solution-Processed , Organic-Semiconductor Thin Films for Transistor Applications. Ph.D. Thesis. Princeton University.: US. Graphics thanks to Anna Hailey

TES ADT and Guiding Crystallization Utilizing differences in TES ADT growth rate on SIO2 vs PFBT-treated Au, growth can be specified along channels. Guiding crystallization allows us to pattern TES ADT into predefined pathways which can potentially have applications in organic electronics. PREFERENTIALLY FOLLOWS THE SILICON Lee, Stephanie. (2012). Processing-Structure- Function Relationships In Solution-Processed , Organic-Semiconductor Thin Films for Transistor Applications. Ph.D. Thesis. Princeton University: US.

My Project What are the limits to guiding growth of TES ADT on patterned substrates? What is the smallest feature size that we can pattern with TES ADT? By understanding more about the growth of TES ADT in channels, we hope to pattern electronics in more elaborate and efficient ways to create new devices and save energy.

Haataja’s Group Predictions Sri Muralidharan’s PhD Thesis: V denotes the growth rate, M denotes mobility , Γ denotes interfacial forces, E denotes the bulk driving force of crystallization, κ denotes interfacial curvature, and w denotes channel width. He predicted that there would be Muralidharan, Srevatsan. (2012). Continuum Studies of Microstructure Formation in Metallic and Organic Thin Films. Ph.D. Thesis. Princeton University: U.S.

TES ADT Growth in Channels 1000um

TES ADT Growth into Corners 1000um

Instantaneous Velocity vs. 1/(width of pattern at growth front) Alta Fang’s Predictions No TES ADT Leaking Out of Corner: TES ADT Leaking Out of Corner: The crystal growth outside of the pattern will always drag the crystal growth front up and over the corner. Instantaneous Velocity vs. 1/(width of pattern at growth front) Alta realized that Sri made assumption It does go over the corner like what we saw because the growth front outside the channel drags the crystal up and over the corner At some point in this graph it is no longer linear because the crystal growth front is larger than the width of the pattern and it asymptotically grows to the rate at which TES ADT is growing on the PFBT treated gold In the portion where the growth front is less than the width of the patterned corner, the trend is linear and we can extrapolate this to find the smallest width of the pattern where we can control the growth of TES ADT

Results: Different Corners Critical Widths: 1.7 um, 2.0 um, 2.5 um

Results: Channel and Corner Data Combined ADD RATIO OF G/E (v=4, w=2) Using the predicted equation, the averaged critical channel width is 2 um.

Closing Remarks - Learned new lab techniques, data analysis skills, and the fundamentals of day-to-day laboratory research - Gained a new perspective on the vast amount of applications of chemical engineering in scientific research - Looking forward to using what I learned this summer in future independent work!

Special Thanks to: