Organic semiconductors enable new and low-cost modes of fabrication for transistors, solar cells, and sensors. The key enabling attribute of organic semiconductors is their solubility in common solvents, which permits deposition by printing processes, but requires that the semiconductor microstructure develop dynamically as an applied solution dries. The resultant microstructure depends on the deposition method, solvent, drying rate, and substrate characteristics. The nanoscale polycrystalline films that are formed can have microstructure variations over length scales ranging from the intermolecular (sub-nanometer) to the device (millimeter) and these variations can strongly influence device performance. This opportunity involves correlating organic semiconductor primary chemical structure, formulation, and processing to the spatially resolved development of microstructure for a series of recently developed polymer semiconductors with transistor performance comparable to amorphous silicon. Measurement tools will include electron microscopies, selective area diffraction, and scanning probe techniques. The study will focus on nucleation and growth mechanisms, the nature of grain boundaries, and behavior at interfaces with dielectrics and conductors. These measurements will complement the ongoing development of microstructure models based on whole-film techniques such as grazing-incidence x-ray diffraction and polarized photon absorption spectroscopies. Correlating spatially resolved microstructure to transistor characteristics such as carrier mobility will inform the rational design of the next generation of organic semiconductor materials and processes.

 

key words

Crystallization; Diffraction; Microscopy; Nanostructure; Organic electronics; Polymer; Semiconductor;

Citizenship:  Open to U.S. citizens

Level:  Open to Postdoctoral applicants