Center for Self-Assembled Organic Electronics

Despite tremendous advances in controlling self-assembly of organic molecules, the impact on high-performance organic electronic materials has been limited. The challenge lies in the stiff conformations and complex phase behavior of conjugated molecules and polymers, including liquid crystalline interactions and phases that complicate the control of domain sizes and interface structures. As such, there is a tremendous opportunity to design materials that exploit these factors to control self-assembly in the active layer of devices. Our recent advances in theoretical descriptions of interaction parameters, chain conformations and liquid crystallinity of stiff molecules uniquely position us to develop new ways to control the microstructure. We will demonstrate systematic control and full characterization of donor and acceptor interfaces of OPV materials composed of high-performance polymers and state of the art non-fullerene acceptors. These will be used to train multi-scale tight-binding models that are coupled to universal descriptions of stiff polymers at interfaces to build predictive design rules about how molecular structure influences self-assembly and guide further development of high performance OPV devices.Flexible and light-weight electronics and solar cells provide a promising solution to the needs of the modern military deployed around the globe, including wearable electronics, underwater power, and light-weight power generation. We thus propose to demonstrate key advances in self-assembly of conjugated molecules and polymers in the context of organic electronics, with a special emphasis on solar cells. Specifically, we propose that the synthetic and structural versatility of our recently developed non-fullerene acceptors provides a pathway to ideal blend morphologies, for design of block copolymers and oligomers to control the mesoscale and interfacial structure, and for programmable hydrogen bonding units to tune self-assembly. In addition to designing chemical structures that drive systems towards thermodynamically stable states, we will map the interplay between miscibility and crystallization through time-temperature-transformation diagrams, which represent the morphological evolution of complex mixtures used in organic solar cells. Thus, we are poised to demonstrate new opportunities in chemical design to enable robust processing of binary and multicomponent solar cells, by leveraging our recently developed flow-coating approaches, our universal descriptions of the dynamics of stiff polymers, and our high throughput characterization and spectroscopy methods that will guide machine learning approaches to identify predictive design rules.The Center will focus on elucidating the factors that govern OPV device performance, to design strategies for controlling the morphology at interfaces and in the bulk. We propose that progress in these areas will be accelerated by organizing the work around five key questions:1. What is the optimum degree of order within donor and acceptor domains, what is the optimum miscibility, and how are these linked to the molecular structure?2. How to design donor-acceptor interfaces to maximize both photocurrent and photovoltage?3. Can specific interactions, such as covalent bonds between donor-acceptor molecules or hydrogen bonds, generate self-assembled surfactants to stabilize the D-A interface?4. What is the morphology of champion multicomponent cells, and what morphology is ideal?5. How to tune molecular structure to widen the processing parameter space suitable for high performance devices?