Princeton University

School of Engineering & Applied Science

Formation of Long Range Ordered Organic Thin Films and their Impact on Solar Cell Energy Loss

Michael Fusella
Engineering Quadrangle B327
Friday, November 3, 2017 - 9:00am to 10:30am

With a growing global population and increasing demand for modern technologies from developing countries, energy production is set to be one of the most important issues in the twenty-first century; one that must be met in an economical and environmentally responsible way for the sake of present and future generations. Toward this end, researchers have sought to replace the bulky, heavy, and expensive-to-install PV modules based on silicon today with lightweight, flexible PVs based on abundant and inexpensive organic materials (i.e., OPVs).
While these are extraordinary promises, OPVs today have not yet been able to achieve the stable lifetimes and power conversion efficiencies necessary to make them commercially viable, primarily since most organic thin films today are disordered. While the practical aspirations of OPVs dictate that thin films be utilized, organic bulk single crystals have revealed remarkable optical and electrical properties that show dramatically improved performance compared to their disordered counterparts.
The primary thrust of this thesis is to unite the enhanced performance of crystalline organic materials with the practicality of thin films. We introduce a facile fabrication technique to turn as-deposited amorphous thin films into ones that are highly crystalline with macroscopic crystalline domains. We then study the practical benefit of thickness tunability these crystalline films possess via an investigation of subsequent adlayer growth atop the crystalline template. Finally, we show how a highly crystalline OPV utilizing these fabrication techniques reveals high-performance physics akin to inorganic solar cells and discuss how to unlock these performance enhancements in other OPV materials systems.