| 1. |
- Adamczak, Desiree, et al.
(författare)
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Influence of synthetic pathway, molecular weight and side chains on properties of indacenodithiophene-benzothiadiazole copolymers made by direct arylation polycondensation
- 2021
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7534 .- 2050-7526. ; 9:13, s. 4597-4606
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Tidskriftsartikel (refereegranskat)abstract
- Atom-economic protocols for the synthesis of poly(indacenodithiophene-alt-benzothiadiazole) (PIDTBT) are presented in which all C-C coupling steps are achieved by direct arylation. Using two different synthetic pathways, PIDTBT copolymers with different side chains (hexylphenyl, octylphenyl, dodecyl, methyl/2-octyldodecylphenyl, 2-octyldodecylphenyl/2-octyldodecylphenyl) and molecular weight (MW) are prepared. Route A makes use of direct arylation polycondensation (DAP) of indacenodithiophene (IDT) and 4,7-dibromo-2,1,3-benzothiadiazole (BTBr2) leading to PIDTBT in high yields, with adjustable MW and without indications for structural defects. Route B starts from a polyketone precursor also prepared by DAP following cyclization. While route B allows introduction of asymmetric side chains at the IDT unit, polymer analogous cyclization gives rise to defect formation. The absorption coefficient of PIDTBT with alkylphenyl side chains made by route A increases with MW. Field-effect hole mobilities around similar to 10(-2) cm(2) V-1 s(-1) are molecular weight-independent, which is ascribed to a largely amorphous thin film morphology. PIDTBT with linear dodecyl side (C12) chains exhibits a bathochromic shift (20 nm), in agreement with theory, and more pronounced vibronic contributions to absorption spectra. In comparison to alkylphenyl side chains, C12 side chains allow for increased order in thin films, a weak melting endotherm and lower energetic disorder, which altogether explain substantially higher field-effect hole mobilities of similar to 10(-1) cm(2) V-1 s(-1).
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| 2. |
- Atxabal, Ainhoa, et al.
(författare)
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Energy Level Alignment at Metal/Solution-Processed Organic Semiconductor Interfaces
- 2017
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 29:19
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Tidskriftsartikel (refereegranskat)abstract
- Energy barriers between the metal Fermi energy and the molecular levels of organic semiconductor devoted to charge transport play a fundamental role in the performance of organic electronic devices. Typically, techniques such as electron photoemission spectroscopy, Kelvin probe measurements, and in-device hot-electron spectroscopy have been applied to study these interfacial energy barriers. However, so far there has not been any direct method available for the determination of energy barriers at metal interfaces with n-type polymeric semiconductors. This study measures and compares metal/solution-processed electron-transporting polymer interface energy barriers by in-device hot-electron spectroscopy and ultraviolet photoemission spectroscopy. It not only demonstrates in-device hot-electron spectroscopy as a direct and reliable technique for these studies but also brings it closer to technological applications by working ex situ under ambient conditions. Moreover, this study determines that the contamination layer coming from air exposure does not play any significant role on the energy barrier alignment for charge transport. The theoretical model developed for this work confirms all the experimental observations.
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