(Invited) accelerating Polymer Discovery for Multifunctional Polymer Thin Films: High-Throughput Characterization

Abstract

Identifying new formulations of polymers that have multiple highly tuned properties is a grand challenge of materials development. This is especially important in polymer thin film devices where several distinct transport properties must be controlled. For instance, solid-state battery electrolyte materials must be conductive to ions, but remain electronically insulating. In order to achieve the materials advances needed to transform the use of such polymer thin films, new paradigms of accelerated materials development are needed.In this talk, we discuss our recent efforts to accelerate the development of advanced polymer thin film materials for energy applications. A crucial feature of accelerating the discovery of high performing formulations and processing conditions is a rapid means to assess the properties of polymer films with spatial resolution commensurate with nanoscopic defects and throughput that can accommodate macroscopic devices. We initially focus on the challenge of verifying that films are electrically insulating. Maintaining electrical insulation across large films is a particularly insidious challenge as small “pin-hole” defects can result in an entire device failing. We explore an optical method to detect and characterize conductive defects based upon the electrochemiluminescence of luminol. In particular, when a voltage is applied to a conductive surface that is protected by a nominally insulating film, regions where the film is not present or is electrically conductive will result in the local generation of light. A major virtue of this approach is that the minimum detectable feature is not directly determined by the wavelength of light or the optical magnification in use, but rather the intensity of light generated per unit area on the surface. To explore this approach, we conduct an extensive series of optimization experiments to maximize the intensity of light generated by electrochemiluminescence by adjusting the timing, voltage, and solution properties. The result of this optimization is that lines narrower than 100 nm are readily detectable using this method. Finally, we present efforts to use this approach to screen centimeter-square areas to find and characterize nanoscale defects.Looking beyond the important task of characterizing films at high throughput, we conclude the talk with a discussion of how this approach fits in a broader materials discovery pipeline. In particular, recent years have seen a number of examples of autonomous experimentation systems that combine automation to perform experiments and machine learning to select experiments to vastly increased the speed at which knowledge is gained. The reported high-throughput analytical process is anticipated to form an important link in this process by providing a path to rapidly and effectively screening films for electrical properties.