Advanced Functional Materials and Devices (AFMD) Group

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Limiting factors for charge generation in low-offset fullerene-based organic solar cells

Authors:

Anna Jungbluth, Eunkyung Cho, Alberto Privitera, Pascal Kaienburg, Andreas Lauritzen, Thomas Derrien, Sameer Kesava, Irfan Habib, Veaceslav Coropceanu, Jean-Luc Bredas, Moritz Riede
More details from the publisher

Pressure-Transferred components

503450223

Authors:

MG Christoforo, MD McGehee, A Salleo, CD Bailie

The role of charge recombination to spin-triplet excitons in non-fullerene acceptor organic solar cells

Authors:

Alexander J Gillett, Alberto Privitera, Rishat Dilmurat, Akchheta Karki, Deping Qian, Anton Pershin, Giacomo Londi, William K Myers, Jaewon Lee, Jun Yuan, Seo-Jin Ko, Moritz K Riede, Feng Gao, Guillermo C Bazan, Akshay Rao, Thuc-Quyen Nguyen, David Beljonne, Richard H Friend

Abstract:

The power conversion efficiencies (PCEs) of organic solar cells (OSCs) using non-fullerene acceptors (NFAs) have now reached 18%. However, this is still lower than inorganic solar cells, for which PCEs >20% are commonplace. A key reason is that OSCs still show low open-circuit voltages (Voc) relative to their optical band gaps, attributed to non-radiative recombination. For OSCs to compete with inorganics in efficiency, all non-radiative loss pathways must be identified and where possible, removed. Here, we show that in most NFA OSCs, the majority of charge recombination at open-circuit proceeds via formation of non-emissive NFA triplet excitons (T1); in the benchmark PM6:Y6 blend, this fraction reaches 90%, contributing 60 mV to the reduction of Voc. We develop a new design to prevent recombination via this non-radiative channel through the engineering of significant hybridisation between the NFA T1 and the spin-triplet charge transfer exciton (3CTE). We model that the rate of the back charge transfer from 3CTE to T1 can be reduced by an order of magnitude, allowing re-dissociation of the 3CTE. We then demonstrate NFA systems where T1 formation is suppressed. This work therefore provides a clear design pathway for improved OSC performance to 20% PCE and beyond.
Details from ArXiV

Wobbe Index Sensor System

11/777,575

Authors:

AJ Knobloch, WJ Antel, JR, MG Christoforo, RM Orenstein

Abstract:

A sensor for measuring Wobbe index of a fuel is provided. The sensor includes a substrate and a diaphragm layer. The diaphragm layer includes a first layer having at least one heating element configured to sense energy content in a fuel, wherein the heating element includes a doped poly-silicon carbide that is disposed on the substrate. The diaphragm layer also includes a second layer including an undoped poly-silicon carbide layer configured to prevent oxidation of the first layer. The sensor further includes a sensing layer having a catalyst suspended in a support structure. The sensor also includes a cavity formed under the diaphragm layer and is configured to provide thermal isolation of the heating element.