Next Generation Molecular Dopants for Organic Electronics: From Fundamentals to New Device Concepts

Approved for Public Release Research problem. Doping of organic semiconductors plays an important and growing role in organic electr,onics, ranging from organic light emitting diodes and organic solar cells to thermoelectrics and bioelectronics. However, unlike Si,,where parts per million dopant concentrations can significantly alter conductivity, doping organic semiconductors with molecular dop,ants typically requires a much higher concentration. Complex interplay between the microstructure, electronic structure and molecula,r interactions of the polymer and dopants has prevented systematic understanding. Progress is largely dependent on heuristically gui,ded, slow, trial-and-error experimentation. Furthermore, only p-type doping has been widely implemented in organic semiconductors, a,nd n-type doping has met with limited success. Thus, developing air-stable n-dopants is an important objective for the field of mole,mized p- and n -doped conducting polymer systems and achieving facile n-doping, 2) extending our recent, paradigm-changing discovery, of air-stable photoredox doping in conjugate polymers (CPs), 3) accelerating the pace of data generation by collaborative workflowi,ntegration of robotic experimentation and machine learning (ML) and artificial intelligence (AI) approaches, 4) creating fundamental, knowledge that informs novel materials synthesis and system optimization, 5) creating new technologies enabled by these advances in,cluding 3D printing and photopatterning of complementary circuits. Our scope extends from fundamental science to demonstration of ne,w device concepts. Approach. This MURI team combines expertise in synthesis (You), characterization (Ginger, So, Ade), processing (A,de, Amassian, You, So, Ginger), computation (Li), robotic experimentation and ML/AI data-analytics (Amassian, Ganapathysubramanian,,asks map direct onto our objectives and are organized in a synergistic fashion around four thrusts: Thrust 1 will develop new materi,als; Thrust 2 will combine ML/AI methods with data-science enabling strategies, including the automation and digitization of certain, experimental workflows [e.g., formulation, processing, characterization methods (general and domain-specific)]; Thrust 3 will yield, deep fundamental understanding; and Thrust 4 will develop and demonstrate novel devices. Information and materials will flow betwee,n all thrusts. Team members have been collaborating extensively for many years, and the established relations will enhance productiv,ity. Outcome: Our work will transform the field by providing comprehensive, in-depth knowledge of doping mechanism and its effects o,n charge carrier density and mobility. It will also bring to maturity a paradigm-changing photoredox strategy recently discovered by, a team member for n-doping in CPs. Overall, our research will result in facile, air-stable n-type doping, improved performance, and, create novel processing routes. Facile n-doping with conventional or photoredox approaches will improve OLEDs and organic solar cel,ls and enable fabrication of devices with complementary/ambipolar transistors and massively serial thermoelectric devices with highv,oltage output. This will enable complex electronics on flexible substrates that can integrate sensing and processing as well as comp,lex opto-electronics. Relevance: Collectively, these resul,ways for applications in portable power (light weight solar and thermoelectric energy harvesting), while improving the energy effici,ency and durability of rugged, lightweight screens and information display devices both in the cockpit and in the field.