Real-Time Studies of Solution-Processed Organic Semiconductor Thin Films

University Of Vermont & State Agricultural College, Burlington VT

Investigators

Abstract

Technical Description: The goal of this research project is to understand in detail and to control molecular self-organization processes, utilizing a simple thin film deposition instrument, the "hollow pen writer," for depositing 10 - 100 nanometer thin films of small-molecule organic semiconductors from solution. The hollow pen writer provides a surprising degree of control over the properties of organic semiconductor thin films, in some ways far surpassing the results obtainable with conventional vapor deposition. The research team utilizes this method to study the relationships between process parameters and film properties, such as crystalline grain structure and grain boundary density. These studies feature real-time analysis techniques such as optical video microscopy and synchrotron x-ray diffraction, which are necessary in order to follow crystallization processes on time scales from milliseconds to minutes and to monitor and distinguish molecular short-range order versus long-range order. In addition, charge carrier transport in test devices such as organic field effect transistors are studied as a function of grain structure and built-in or applied stress. Non-Technical Description: Organic semiconductors are designed at the molecular level to exhibit useful properties, and they promise the realization of a new generation of electronic circuits and solar cells. This research activity addresses a key step in optimal utilization of organic electronic materials, the organization of individual molecules into crystalline form through controllable processes such as coating from a liquid solution into a thin layer. Packing of molecules into crystals as well as the structure of crystal boundaries profoundly affects the properties of thin films. The research team seeks to understand the mechanisms inherent to solution processing in order to evaluate, understand, exploit, and predict the potential of new functional materials that are being synthesized at an ever-increasing rate. The societal impact of the research is amplified by innovative teaching methods and by pursuing community outreach objectives, including: an undergraduate teaching lab to make organic solar cells, enhanced through online tools for analyzing and discussing results; lectures and demonstrations designed to engage the public in a discussion of the science and applications of energy, light, materials, and nano-materials.