- Post Doctoral
MIT Unit Affiliation:
- Chemical Engineering
Post Doc Sponsor / Advisor:
Date PhD Completed:
Top 3 Areas of Expertise:
My research focuses on understanding and controlling material phase changes using microfluidic techniques. Specifically, I am interested in how crystal growth and polymorphism is impacted by different mechanisms such as supersaturation, confinement, reactions where the molecule is a product/byproduct, etc. My doctoral research focused on the crystallization of organic semiconductors (OSCs) and how various coating techniques can impact the crystallization behavior and the eventual electronic properties of OSCs. My research provided guidelines for controlling polymorphism in OSCs through processing parameters as well as fundamental understanding of how confinement affect large area crystal film polymorphism. My postdoctoral work is focused on improving solid handling during continuous flow synthesis by controlling crystal growth of byproducts. To minimize clogging in the microreactor during chemical synthesis, understanding of the crystal growth profile of the solid, the fluid flow dynamics and the reaction kinetics is necessary. I am also exploring the rapid prototyping of microreactors through the use of additive printing technologies.
My future research will focus on utilizing my background in chemical engineering and material science to provide a fundamental understanding of phase change in organic materials, and how equilibrium and kinetic conditions tilt the system towards various stabilized phases. This knowledge will be used to generate applications for phase control in organic systems that span pharmaceutical drug product synthesis, formation and delivery, and energy applications including catalysis, photovoltaics and energy storage.
Expected End Date of Post Doctoral Position:
1. Extending microreactor lifetime during continuous flow synthesis through control of solid formation
2. Rapid prototyping of reactors using additive printing
Circuits based on organic semiconductors (OSCs) are being currently explored for flexible, transparent and low-cost electronic applications. However, to realize such applications, the charge transport performance of OSCs in thin film transistors (TFTs) must be improved. Using a solution processing method called solution shearing, we were able to create metastable polymorphs of various OSCs and improve the electronic performance. This is the first time industrially friendly coating processes have been utilized to change the molecular packing of OSCs. Changing the molecular packing to form metastable polymorphs through solution processing allows researchers to complement traditional synthetic methods to generate high performance OSCs.
The first part of my research work details the use of solution shearing to increase the mobility of small molecular OSCs. The model OSC 6,13-bis(triisopropylsilylethynyl) pentacene (TPn) is used as the model compound for our study, and various metastable polymorph are created through solution processing. In order to study crystallization of OSCs during solution shearing, my research extended to constructing a miniaturized solution shearing machine to be used in-situ at synchrotron facilities. We obtained high speed (100 frames/s), in-situ images of metastable crystal growth using a microbeam (20 μm) grazing incidence X-ray diffraction (GIXD) method. Using knowledge from these experiments, we were able to obtain design rules for creating lattice strain and polymorphism using other solution processing techniques. Finally, our research has brought the use of lattice strain closer industrial use through the use of selective deposition of OSCs. Industrial applications of lattice strained organic TFTs requires that the organic TFTs are patterned. We have developed a surface functionalization procedure that utilizes hydrophobic/hydrophilic interactions to isolate lattice strained OSCs.
In summary, we have shown that high performance, metastable polymorphs of various organic semiconductors can be fabricated through solution processing methods, and the underlying reasons for polymorphism is explained through the use of in-situ X-ray diffraction techniques.
Top 5 Awards and honors (name of award, date received):
5 Recent Papers:
Giri, G., Li, R., Smilgies, D.M., Li, E.Q., Chiu, M., Lin, D.W., Allen, R., Diao, Y., Mannsfeld, S.C.B., Thoroddsen, S.T., Bao, Z. and Amassian, A. (2014) “One-Dimensional Self-Confinement Promotes Polymorph Selection in Large Area Organic Semiconductor Thin Films.” Nature Communications. 5, 3573. Online View. http://www.nature.com/ncomms/2014/140416/ncomms4573/full/ncomms4573.html
Yuan, Y., Giri, G., Ayzner, A., Zoombelt, A.P., Mannsfeld, S.C.B., Chen, J., Huang, J. and Bao, Z. (2014) “Solution-processed Ultra-High Mobility Transparent Organic Thin Film Transistors with a Meta-stable Semiconductor Channel.” Nature Communications¸ 5, 3005. Online View. http://www.nature.com/ncomms/2014/140108/ncomms4005/full/ncomms4005.html...
Giri, G.*, Park, S.*, Vosgueritchian, M., Shulaker, M.M. and Bao, Z. (2013) “High Mobility, Aligned, Crystalline Domains of TIPS-pentacene with Strained Lattice through Lateral Confinement of Crystal Growth.” Adv. Mater. 26 (3): 487-493. http://onlinelibrary.wiley.com/doi/10.1002/adma.201302439/abstract
Diao, Y., Tee, B.C.K., Giri, G., Xu, J., Becerril, H.A., Stoltenberg, R.S., Lee, T.H., Xue, G., Mannsfeld, S.C.B. and Bao, Z. (2013) “Printing Highly Aligned, Large Single-crystalline Domain Organic Semiconductors.” Nature Materials, 12 : 665-671. http://www.nature.com/nmat/journal/v12/n7/abs/nmat3650.html
Giri, G., Verploegen, E., Mannsfeld, S.C.B., Atahan-Evernk, S., Kim, D.H., Lee, S.Y., Becerril, H.A., Aspuru-Guzik, A,, Toney, M.F. and Bao, Z. (2011). "Tuning Charge Transport in Solution-sheared Organic Semiconductors using Lattice Strain." Nature 480 (7378): 504-508. http://www.nature.com/nature/journal/v480/n7378/abs/nature10683.html