Beyond Silicon: Modeling the Materials Behind the Future of Electronics

From smartphones to solar panels, today’s technology relies heavily on silicon. The next generation of electronics, like wearable sensors and foldable screens, may depend on an entirely different class of materials: organic semiconductors.  

To help make that future into a reality, Toulik Maitra, a Ph.D. student in chemical engineering at the University of California, Davis, is using computational modeling to understand how these materials behave at the molecular level. His work recently expanded through an international collaboration at Germany’s Max Planck Institute, a global leader in polymer and organic electronics research.  

“Whenever we think about futuristic devices, we think about chips in our brain, putting devices in our bodies, or phones with curved screens,” Maitra said. “All of those applications have organic semiconductors in them.”    

An early version of Maitra's work is available on arXiv as the international team prepares it for peer review. 

Beyond Silicon 

Silicon is an excellent semiconductor, capable of switching between conducting and blocking electricity. However, silicon atoms are locked together by covalent bonds, making them strong but also rigid.  

Organic semiconductors, on the other hand, are carbon-based materials that can perform the same electronic functions as silicon but are more flexible because their molecules are held together by weak attractions called van der Waals forces.  

“It’s the same force that lets a gecko stick to a smooth wall without any glue,” Maitra says.  

That flexibility also makes the materials much more difficult to model accurately. 

“Due to van der Waals forces, at room temperature, the molecules vibrate, causing each electron cloud to shift in response to its neighbors, or polarization,” Maitra said. “It has a large effect on how charges move through the material and interact with light.”  

Capturing this behavior accurately in computer simulations is difficult, slowing the design of new organic semiconductor materials. Maitra’s goal is to computationally model the molecular behavior to design better materials before anyone steps into a lab.  

A Promising New Framework  

During a six-month appointment as a visiting fellow at the Max Planck Institute for Polymer Research in Mainz, Germany, Maitra and his collaborators set out to capture how shifts in polarization affect charge transport and light interactions.  

The international team developed a new computational framework that predicts how individual atoms respond to their molecular surroundings, enabling simulations to more accurately reflect the behavior of organic semiconductors in the real world. 

The framework accounts for the unique environment surrounding each atom. It has proven more accurate than conventional methods, which assign the same electronic properties to broad categories of atoms.  

It also accurately models molecules in their neutral, charged and excited states — the same conditions they experience inside a working electronic device. When combined with machine learning, the framework can quickly predict these properties for new molecules, enabling researchers to identify promising materials before synthesizing them in the laboratory. 

From Simulation to OLEDs 

Maitra is already applying these improved modeling techniques to his doctoral research in the laboratory of Adam Moulé, professor of chemical engineering at UC Davis. There, he studies organic semiconductor materials for organic light-emitting diodes, or OLEDs, with a particular focus on thermally activated delayed fluorescence, or TADF, emitters and high-mobility molecules. 

Currently, the highest-efficiency OLED displays often rely on rare metals such as iridium and platinum to produce bright, energy-efficient light. TADF materials offer a promising alternative, achieving similar performance with entirely organic molecules.  

By more accurately predicting how those molecules will behave before they are synthesized, Maitra hopes to help researchers accelerate the search for efficient OLED materials that reduce dependence on expensive, rare-earth materials. 

"I am always excited to move the field forward," Maitra said. "If this method works, then the next thing you want to model — device performance or vibration analysis — can be done in a better way." 

Investing in the Future

Maitra will be able to continue his collaboration with the Max Planck Institute at UC Davis in the Moulé Lab thanks to a UC Davis Dissertation Fellowship, which is awarded by UC Davis Graduate Studies to support a Ph.D. student for a year toward the end of their academic career.   

The fellowship gives Maitra the time to focus on publishing his research, completing his dissertation and preparing for a career advancing organic semiconductor technologies. 

"I believe in this field,” Maitra said. “Working with organic semiconductors will make a better future."