Effect of the Terminal Acceptor Unit on the Performance of Non-Fullerene Indacenodithiophene Acceptors in Organic Solar Cells

Six new bio-inspired flavylium salts were synthesized and investigated by a combined computational and experimental study for dye-sensitized solar cell applications. The compounds were characterized by FT–IR, UV–Vis, NMR spectroscopy, and LC–MS spectrometry techniques. The pH-dependent photochromic properties of the flavylium dyes were investigated through a UV–Vis spectroscopy study and revealed that they follow the same network of chemical reactions as anthocyanins upon pH changes. The structural and electronic properties of the dyes were investigated using density functional theory (DFT) and time-dependent density functional theory (TD–DFT). Geometry optimization calculation revealed that all dyes, regardless of the specie, flavylium cations or quinoidal bases, present a planar geometry. The photovoltaic performances of the dyes, in both flavylium and quinoidal base forms, were evaluated by the HOMO and LUMO energies and by calculating the light-harvesting efficiencies, the free energy change of electron injection, and the free energy change regeneration. The MO analysis showed that all dyes can inject electrons into the conduction band of the TiO2 upon excitation and that the redox couple can regenerate the oxidized dyes. The results obtained for the free energy change of electron injection suggest that the quinoidal bases should inject electrons into the semiconductor more efficiently than the flavylium cations. The values for the free energy change regeneration showed that the redox electrolyte can easily regenerate all dyes. Dipole moment analysis was also performed. DSSCs based on the dyes, in both flavylium and quinoidal base forms, were assembled, and their photovoltaic performances were evaluated by measuring the open-circuit voltage, the short circuit current density, the fill factor, and the energy conversion efficiency. Results obtained by both experimental and computational studies showed that the overall performances of the DSSCs with the quinoidal forms were better than those obtained with the flavylium cations dyes.

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“…Large ∆µ ge values, associated with enhanced polarizability, enable appropriate charge generation processes [ 64 , 65 ].…”

Section: Resultsmentioning

confidence: 99%

Experimental and Computational Studies on Bio-Inspired Flavylium Salts as Sensitizers for Dye-Sensitized Solar Cells

et al. 2022

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“…For the synthesis of the RSQ1 squaraine, we replaced the dicyanomethylene group with the even stronger rhodanine acceptor (Scheme 1). [40] Experimental details for the RSQ1 synthesis are compiled in the Supporting Information. Scheme 1 also includes the chemical structures of the dyes SQ1 and DCSQ1.…”

Section: Synthesis and Molecular Propertiesmentioning

confidence: 99%

Squaraine Dyes for Single‐Component Shortwave Infrared‐Sensitive Photodiodes and Upconversion Photodetectors

Hu,

Nüesch,

Giavazzi

et al. 2023

Advanced Optical Materials

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Sensitive detection of shortwave infrared (SWIR) light using organic dyes will be a significant advance toward many applications in industry and research. Furthermore, from a fabrication and optimization view, photogeneration of charges in diodes consisting of a single dye layer will be highly attractive. However, SWIR dyes are scarce and organic photodiodes usually utilize a donor–acceptor materials combination to split excitons into charges. Here, it is demonstrated that single‐component layers of several SWIR squaraine dyes operate as efficient photodetectors, with peak external quantum efficiency > 40% beyond 1000 nm and sensitivity out to 1300 nm. Photocurrents show a superlinear dependence on reverse bias. It is shown that this results from a field‐assisted exciton dissociation mechanism, and not from field‐dependent charge injection or extraction. SWIR photodiodes are combined with organic light‐emitting diodes to fabricate upconversion photodetectors – devices that convert SWIR photons directly into visible light. Upconverters are characterized by a low turn‐on voltage (1.5 V) and a high luminance contrast (on‐off ratio 16 000) and SWIR‐to‐visible (λ = 575 nm) photon conversion efficiency (1.85%). Upconversion photodetectors emerge as a promising alternative to the current inorganic‐based imaging technology.

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Effect of the Terminal Acceptor Unit on the Performance of Non-Fullerene Indacenodithiophene Acceptors in Organic Solar Cells

Cited by 2 publications

References 36 publications

Experimental and Computational Studies on Bio-Inspired Flavylium Salts as Sensitizers for Dye-Sensitized Solar Cells

Experimental and Computational Studies on Bio-Inspired Flavylium Salts as Sensitizers for Dye-Sensitized Solar Cells

Squaraine Dyes for Single‐Component Shortwave Infrared‐Sensitive Photodiodes and Upconversion Photodetectors

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