Approaching Theoretical Voltage Limits in Organic Photovoltaics with Molecularly Tailored Film Morphology FY2019-000133-AS
Abstract
Organic photovoltaics have the unique potential to serve as low cost power sources in DoDmissions ranging from high-endurance UAVs to portable power in the field. This potential arisesfrom their unrivalled power/weight ratios, and their inherently flexible, conformal, and heavymetal free thin films that can enable novel geometries and form factors. After stagnating in the 11-12% efficiency range, OPV efficiencies are rising again following the introduction of newfamilies of non-fullerene acceptors (NFAs), and are now exceeding 16% in single junction devices, and over 17% in tandem structures. Nevertheless, these values are still well below the theoretical Shockley-Queisser limit, with non-radiative recombination losses posing a key challenge to the technology. To address this challenge, this proposal will study the factors that control nonradiative recombination in order to overcome the barrier non-radiative recombination presents to achieving theoretical device efficiencies.The proposal combines molecular synthesis with photophysical studies, building on preliminarydata that points to complementary strategies of molecular design, and morphology control inorder to maximize radiative recombination while minimizing non-radiative losses.The specific objectives of the proposal are to:1) synthesize new generations of inherently luminescent electron donor and acceptor species,focusing on optimization of intramolecular charge transfer character, molecular symmetry, andstiffness2) pursue structural control over non-radiative recombination in blends by controllingelectron-phonon coupling via tailoring of the solid state morphology, achieving both a betterfundamental understanding of how solid state morphology controls non-radiative losses, and how to reduce such losses3) use model systems to test the fundamental limits of OPV efficiency. Specifically, to explorepathways to circumvent Marcus-theory-based limits on non-radiative losses by leveragingsynthetic efforts described in objectives (1) and (2) and using immediately available model systems to: make direct experimental measurements of LE/CT mixing in the context of 3-state models, in different compounds, while correlating these experimental values of LE/CT mixing with measurements of radiative efficiency and internal quantum efficiency (IQE) to better understand the implications and design rules of LE/CTmixing, (b) use of TADF systems as models to probe the limits of suppressing of non-radiative recombination in organics, and (c) more carefully assess the role of driving force in charge separation.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 29, 2020
- Source ID
- N000142012191
Entities
People
- David Ginger
Organizations
- Office of Naval Research
- United States Navy
- University of Washington