Design of donor–acceptor star-shaped oligomers for efficient solution-processible organic photovoltaics

This contribution describes recent progress in the design, synthesis and properties of solution-processible star-shaped oligomers and their application in organic photovoltaics. Even though alternative chemistry has been used to design such oligomers, the most successful approach is based on a triphenylamine donor branching center, (oligo)thiophene conjugated spacers and dicyanovinyl acceptor groups. These are mainly amorphous low band-gap organic semiconductors, though crystalline or liquid crystalline ordering can sometimes be realized. It was shown that the solubility, thermal behavior and structure of such molecules in the bulk strongly depend on the presence and position of alkyl groups, as well as on their length. The photovoltaic properties of solution-processed molecules of this type are now approaching 5% which exceeds those of vacuum-sublimed devices. The design rules and future perspectives of this class of organic photovoltaic molecules are discussed.

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Scattering Techniques for Mixed Donor-Acceptor Characterization in Organic Photovoltaics

Materials Horizons ◽

10.1039/d1mh01219c ◽

2021 ◽

Author(s):

Thomas Chaney ◽

Andrew Levin ◽

Sebastian Schneider ◽

Michael F. Toney

Keyword(s):

Power Conversion Efficiency ◽

Conversion Efficiency ◽

Organic Photovoltaics ◽

Bulk Heterojunction ◽

Power Conversion ◽

Organic Photovoltaic ◽

Precise Control ◽

Active Layers ◽

Complex Morphology ◽

Donor Acceptor

Precise control of the complex morphology of organic photovoltaic bulk heterojunction (BHJ) active layers remains an important yet challenging approach for improving power conversion efficiency. Of particular interest are the...

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Free Charge Photogeneration in a Single Component High Photovoltaic Efficiency Organic Semiconductor

10.21203/rs.3.rs-376343/v1 ◽

2021 ◽

Author(s):

Justin Hodgkiss ◽

Michael Price ◽

Paul Hume ◽

Aleksandra Ilina ◽

Isabella Wagner ◽

...

Keyword(s):

Organic Semiconductors ◽

Organic Photovoltaics ◽

Photovoltaic Cells ◽

Single Component ◽

Dielectric Constants ◽

Organic Photovoltaic ◽

Free Charge ◽

Photovoltaic Devices ◽

Organic Photovoltaic Devices ◽

Charge Generation

Abstract Organic photovoltaic cells promise cheap, flexible and scalable solar energy. Whereas light directly generates free charges in silicon photovoltaic cells, bound electron and hole pairs known as excitons are understood to be the primary excitations in organic semiconductors due to their low dielectric constants. These excitons must then be split apart at molecular heterojunctions in order to extract current. Recent record efficiency organic photovoltaics utilise the small molecule, Y6, as a key component in the photon-absorbing blend layer. This molecule and its analogues – unlike previous organic semiconductors – have both low band-gaps and high dielectric constants. Here we show that, in a neat film of Y6, these factors lead to intrinsic free charge generation without the need for a molecular heterojunction to split the exciton. We use a suite of intensity-dependent optical spectroscopy measurements to show that a significant (20-90%) fraction of free charges exist in equilibrium with bound states at light intensity equivalent to 1 sun. Rapid bimolecular charge recombination constrains single component Y6 organic photovoltaic devices to low efficiencies, but this recombination is reduced by the introduction of small quantities of donor polymer. Quantum-chemical calculations reveal charge generation pathways through strong coupling between exciton and CT states, and an intermolecular polarisation pattern that drives exciton dissociation. Our results challenge the understanding of how current record efficiency organic photovoltaics operate, and point towards new future possibilities – offering a molecular picture of intrinsic charge generation as a platform to improve charge yields, and renewing the possibility of efficient single-component organic photovoltaic devices.

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Charge generation in organic photovoltaics: a review of theory and computation

Molecular Systems Design & Engineering ◽

10.1039/c6me00005c ◽

2016 ◽

Vol 1 (1) ◽

pp. 10-24 ◽

Cited By ~ 59

Author(s):

Kenley M. Pelzer ◽

Seth B. Darling

Keyword(s):

Organic Photovoltaics ◽

Charge Separation ◽

Photovoltaic Device ◽

Organic Photovoltaic ◽

Device Performance ◽

Exciton Dissociation ◽

Charge Generation ◽

Computational Approaches ◽

Organic Photovoltaic Device ◽

Donor Acceptor

One of the most important factors in determining organic photovoltaic device performance is the efficiency of exciton dissociation and charge separation at donor/acceptor heterojunctions. This review discusses theoretical and computational approaches to modeling this crucial process of charge generation.

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Tuning the photovoltaic parameters of thiophene-linked donor–acceptor liquid crystalline copolymers for organic photovoltaics

Polymer Chemistry ◽

10.1039/c2py00523a ◽

2012 ◽

Vol 3 (3) ◽

pp. 710 ◽

Cited By ~ 8

Author(s):

Kai Yao ◽

Lie Chen ◽

Yiwang Chen ◽

Fan Li ◽

Xingye Ren ◽

...

Keyword(s):

Organic Photovoltaics ◽

Liquid Crystalline ◽

Donor Acceptor ◽

Photovoltaic Parameters

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Chemical engineering of donor–acceptor liquid crystalline dyads and triads for the controlled nanostructuration of organic semiconductors

CrystEngComm ◽

10.1039/c6ce00365f ◽

2016 ◽

Vol 18 (25) ◽

pp. 4787-4798 ◽

Cited By ~ 21

Author(s):

Yiming Xiao ◽

Xiaolu Su ◽

Lydia Sosa-Vargas ◽

Emmanuelle Lacaze ◽

Benoît Heinrich ◽

...

Keyword(s):

Organic Semiconductors ◽

Liquid Crystalline ◽

Chemical Engineering ◽

Donor Acceptor

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Advances toward the effective use of block copolymers as organic photovoltaic active layers

Polymer Chemistry ◽

10.1039/c7py01878a ◽

2018 ◽

Vol 9 (7) ◽

pp. 795-814 ◽

Cited By ~ 29

Author(s):

V. D. Mitchell ◽

D. J. Jones

Keyword(s):

Block Copolymers ◽

First Principles ◽

State Of The Art ◽

Organic Photovoltaic ◽

Modern State ◽

Future Perspectives ◽

Active Layers ◽

Donor Acceptor ◽

Effective Use

Donor/acceptor block copolymers for organic photovoltaic active layers are discussed from first principles through the modern state-of-the-art and future perspectives.

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Energetic Control of Redox-Active Polymers Towards Safe Organic Bioelectronic Materials

10.26434/chemrxiv.11366186.v1 ◽

2019 ◽

Author(s):

Alexander Giovannitti ◽

Reem B. Rashid ◽

Quentin Thiburce ◽

Bryan D. Paulsen ◽

Camila Cendra ◽

...

Keyword(s):

Molecular Oxygen ◽

Organic Semiconductors ◽

Side Reaction ◽

Semiconducting Polymers ◽

Side Reactions ◽

Redox Active ◽

Donor Acceptor ◽

Electrochemical Devices ◽

Biological Environment ◽

Device Operation

Avoiding faradaic side reactions during the operation of electrochemical devices is important to enhance the device stability, to achieve low power consumption, and to prevent the formation of reactive side‑products. This is particularly important for bioelectronic devices which are designed to operate in biological systems. While redox‑active materials based on conducting and semiconducting polymers represent an exciting class of materials for bioelectronic devices, they are susceptible to electrochemical side‑reactions with molecular oxygen during device operation. We show that this electrochemical side reaction yields hydrogen peroxide (H2O2), a reactive side‑product, which may be harmful to the local biological environment and may also accelerate device degradation. We report a design strategy for the development of redox-active organic semiconductors based on donor-acceptor copolymers that prevent the formation of H2O2 during device operation. This study elucidates the previously overlooked side-reactions between redox-active conjugated polymers and molecular oxygen in electrochemical devices for bioelectronics, which is critical for the operation of electrolyte‑gated devices in application-relevant environments.

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