DMREF: Organic Semiconductors by Computationally-Accelerated Refinement (OSCAR)

Organic semiconductors (OSCs) are at the forefront of next-generation consumer electronics, with new organic light-emitting diode displays appearing yearly. The real need for high-performance OSCs was highlighted at the Consumer Electronics Show in Las Vegas, where press reports emphasized that the future of electronics involved flexible substrates for displays, sensors, or lighting. While OSCs are ideal candidates for such applications, particularly in the area of transistor backplanes for flexible displays, current materials and processes are not yet at the point where high-performance, large-area, low-cost device arrays can be prepared at manufacturing scale at low cost. Manufacturing flexible electronics that meet consumer expectations of price and performance requires improved OSCs with properties that allow large-area deposition using low-cost methods, without decreasing performance. This proposal will develop a multiscale theoretical approach to mine the structure and electronic properties of an established set of crystal structures to predict the functionalization patterns required to achieve the desired electronic performance from a given OSC chromophore. Efforts in parallel will synthesize these predicted targets, as well as optimize and evaluate their use in large-area transistor arrays. Key Words: Organic semiconductor, crystal structure optimization Intellectual Merit : The solid-state order of OSCs is a primary consideration for their performance in devices, yet the ability to predict the crystal structure of even simple organic compounds is still out of reach. However, there are classes of OSCs whose crystal packing is dominated by simple steric effects. By selecting a set of materials with which the PIs have extensive experience in synthesis and device processing, and for which numerous crystal structures already exist, this project will develop computational protocols to determine the degree of perturbation of the solid-state order needed to dramatically enhance electronic performance and the functionalization changes needed to attain this solid-state order. Computational assessments will be validated by molecule synthesis, structural characterization and device screening. Iteration through this process will generate a high-dimensional database that can then be mined to accelerate the development of materials with optimum charge transport. To explore the suitability of new, high-performance materials in low-cost, large-area electronics manufacturing, candidates will be tested in devices fabricated by spray deposition, or by printing techniques. Careful analysis of the resulting films will allow us to further expand our database to consider the impact of process methods on solid-state order. The models developed and tested on known semiconductors will then be applied to new high-performance semiconductor classes to assess the generality of the optimized models. Broader Impacts : Developing computational tools to derive the solid-state order of OSCs will massively accelerate the discovery and deployment of new materials, eliminating the current Edisonian approach of synthesis, purification and device analysis to explore materials space. Refinement of the high-level calculations and generalization of the crystal packing model will make it applicable to materials discovery in a variety of areas, including thin-film transistors, photovoltaics, thermoelectrics and sensors. Students participating in this project will receive training in a highly interdisciplinary project, and will travel to the collaborating groups to learn techniques first-hand from the groups developing them. PIs from this project who are located in Appalachian regions of the U.S. will emphasize the recruitment of students from these rural, under-represented regions to participate in this project. We will also partner with the recent Broadening Participation in Engineering program established at UK to recruit undergraduate researchers. Research in this project will inform the development of new courses at UK and WFU. The outputs of this collaborative project (models, data sets, crystal structures) will all be made freely available from a curated website, to allow other researchers to explore alternative models, or to further refine the models generated here. Finally, the discovery of new high-performance, solution-processable organic semiconductors amenable to large-area device fabrication will enhance manufacturing capabilities, giving impetus for more industries to develop new commercial products involving flexible electronics technology.