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Asymmetric triphenylamine–phenothiazine based small molecules with varying terminal acceptors for solution processed bulk-heterojunction organic solar cells
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. (Bertil Eliasson)ORCID-id: 0000-0001-5746-017X
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
2018 (engelsk)Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, nr 9, s. 6390-6400Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Three compounds consisting of the electron-donating triphenylamine–phenothiazine conjugate backbone and each of the electron-withdrawing groups 3-ethylrhodanine, malononitrile and 1,3-indandione have been synthesized and used as donors in blends with [6,6]-phenyl-C70-butyric acid methyl ester (PC71BM) for organic solar cell devices. After improvements of the active layer structure by a selected donor-to-acceptor weight ratio and a two-step solvent and thermal annealing, the organic solar cells showed power conversion efficiency (PCE) values in the range of 4.79–7.25%. The highest PCE was obtained for the bulk heterojunction device with the indandione compound, which can be attributed to its better absorption profile, higher crystallinity, more balanced electron and hole transport, higher charge collection efficiency and reduced recombination, in comparison with the photovoltaic cells from the other two compounds. DFT-calculated characteristics, absorption spectra and cyclic voltammetry of the compounds, along with X-ray diffraction patterns of the blend films, are used to validate the photovoltaic results.

sted, utgiver, år, opplag, sider
Royal Society of Chemistry, 2018. Vol. 20, nr 9, s. 6390-6400
Emneord [en]
Organic solar cell, asymmetric small molecule donor, charge-transfer compound, bulk heterojunction, solvent annealing, thermal annealing, electron acceptor, power conversion efficiency
HSV kategori
Identifikatorer
URN: urn:nbn:se:umu:diva-144464DOI: 10.1039/C7CP08653AISI: 000429280100040PubMedID: 29441385OAI: oai:DiVA.org:umu-144464DiVA, id: diva2:1180001
Tilgjengelig fra: 2018-02-03 Laget: 2018-02-03 Sist oppdatert: 2018-06-09bibliografisk kontrollert
Inngår i avhandling
1. Molecular design, synthesis and performance evaluation of phenothiazine-based small molecules for efficient organic solar cells
Åpne denne publikasjonen i ny fane eller vindu >>Molecular design, synthesis and performance evaluation of phenothiazine-based small molecules for efficient organic solar cells
2018 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Alternativ tittel[sv]
Design, syntes och utvärdering av fenotiazin-innehållande små molekyler till effektiva organiska solceller
Abstract [en]

Photovoltaics offers one of the most promising routes to generate electricity in a clean way. As an emerging technology in photovoltaics, organic solar cells (OSC) have attracted a great deal of attention owing to their potential low-cost, lightweight, flexibility and solution processability. Although power conversion efficiencies above 12% have been achieved at this date, there is a great interest for new ideal materials to further improve the PCEs and address device durability, which are major concerns for the commercialization of this technology. The main objective of this thesis is to design and synthesize phenothiazine-based conjugate small molecules and explore their use as electron donor components in OSCs. Phenothiazine is a non-planar moiety with unusual “butterfly” type of geometry, which is known to reduce molecular aggregation and intermolecular excimer formation.

In the first study of this thesis, a small molecule based on a cyano-arylenevinylene building block with deep HOMO level was prepared. Although a high open-circuit voltage of 1.0 V was achieved, the tendency of the small molecule to crystallize in the active layer at a higher temperature and with time hindered the attainment of an optimal phase morphology required for the achievement of a higher efficiency. In the second and third studies, phenothiazine was used as a π-system bridge and as a core unit to construct small molecules based on symmetric and asymmetric frameworks with varying terminal electron-withdrawing groups. The electron-withdrawing property of the terminal units was found to have a significant influence on the optical absorption properties, electronic energy levels, molecular ordering, charge carrier mobility and morphology of the resulting active layers. In the fourth study, side-chain modification of the phenothiazine unit of symmetrically configured small molecules with an oxygen-containing (methoxyethoxy ethyl) side chain resulted in the enhancement of the dielectric constant. Although absorption properties were unchanged in solution, a dense π-π stacking was observed in the solid state.

In summary, it is demonstrated that phenothiazine is a promising candidate and worth exploring donor material for OSCs. Its versatility as a π-linker and as a central core unit in symmetric and asymmetric configurations has been explored. The use of nonplanar building blocks such as phenothiazine for the construction of donor materials is an interesting strategy for controlling molecular aggregation and difficult solution processability of small molecules if it is combined with a judiciously designed conjugate backbone.

sted, utgiver, år, opplag, sider
Umeå: Umeå University, 2018. s. 90
Emneord
Organic solar cell, small molecule donors, phenothiazine, power conversion efficiency
HSV kategori
Forskningsprogram
organisk kemi
Identifikatorer
urn:nbn:se:umu:diva-144465 (URN)978-91-7601-835-4 (ISBN)
Disputas
2018-02-28, KBE301 - Lilla Hörsalen, KBC-huset, Umeå, 10:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2018-02-07 Laget: 2018-02-04 Sist oppdatert: 2018-06-09bibliografisk kontrollert

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