(Invited) Structure Measurements for Organic Photovoltaics Manufacturing

Organic photovoltaics (OPV) is a promising candidate technology for the low-cost fabrication of modules to harvest solar energy.  Although OPV technology has significantly matured over the past few years, there remain significant challenges in addressing the gap between lab-scale devices and real manufacturing. Structure-property-performance relationships for OPV devices are still underdeveloped, and relationships based on one system are not necessarily transferrable to new, higher-performance systems. This talk will describe our efforts to develop measurements that support OPV manufacturing. Using a blade coating process as a prototype for slot-die coating, we have developed several techniques to observe the structure of OPV films in-situ as they dry. Our measurements include synchrotron-based X-ray scattering and a variety of optical methods. We use these techniques to identify the mechanisms by which formulation and processing choices influence the nanoscale structure of the films. Several OPV systems will be described including polymer/fullerene, small-molecule/fullerene, and polymer/polymer. Throughout solidification, we can follow the number of phases, their composition, and the extent of order within them. In-situ techniques provide far more information about the solidification process than can be obtained by measuring already-dried films, providing a valuable tool to guide the selection of formulation and processing parameters.