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- Hou, Lintao, et al.
(författare)
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Lateral Phase Separation Gradients in Spin-Coated Thin Films of High-Performance Polymer: Fullerene Photovoltaic Blends
- 2011
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-3028 .- 1616-301X. ; 21:16, s. 3169-3175
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Tidskriftsartikel (refereegranskat)abstract
- In this study, it is demonstrated that a finer nanostructure produced under a rapid rate of solvent removal significantly improves charge separation in a high-performance polymer: fullerene bulk-heterojunction blend. During spin-coating, variations in solvent evaporation rate give rise to lateral phase separation gradients with the degree of coarseness decreasing away from the center of rotation. As a result, across spin-coated thin films the photocurrent at the first interference maximum varies as much as 25%, which is much larger than any optical effect. This is investigated by combining information on the surface morphology of the active layer imaged by atomic force microscopy, the 3D nanostructure imaged by electron tomography, film formation during the spin coating process imaged by optical interference and photocurrent generation distribution in devices imaged by a scanning light pulse technique. The observation that the nanostructure of organic photovoltaic blends can strongly vary across spin-coated thin films will aid the design of solvent mixtures suitable for high molecular-weight polymers and of coating techniques amenable to large area processing.
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| 2. |
- Li, Weiwei, et al.
(författare)
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The Effect of additive on performance and shelf-stability of HSX-1/PCBM photovoltaic devices
- 2011
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Ingår i: Organic electronics. - : Elsevier Science B.V., Amsterdam.. - 1566-1199 .- 1878-5530. ; 12:9, s. 1544-1551
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Tidskriftsartikel (refereegranskat)abstract
- How 1,8-diiodooctane (DIO) enhances performance of polymer solar cells based on polymer HXS-1 and fullerene [6,6]-phenyl C(71)-butyric acid methyl ester (PC(71)BM) from 3.6% to 5.4% is scrutinized with several techniques by comparing devices or blend films spin-coated from dichlorobenzene (DCB) to those from DCB/DIO (97.5:2.5 v/v). Morphology of blend films is examined with atomic force microscopy (AFM), transmission electron microscopy (TEM) and electron tomography (3-D TEM), respectively. Charge generation and recombination is studied with photoluminescence, and charge transport with field effect transistors. The morphology with domain size in 10-20 nm and vertical elongated clusters formed in DIO system is supposed to facilitate charge transport and minimize charge carrier recombination, which are the main reasons for enhancing power conversion efficiency (PCE) from 3.6% (without DIO) to 5.4% (with DIO). Furthermore, a two year inspection shows no significant impact of DIO on the shelf-stability of the solar cells. No visible degradation in the second year indicates that the morphology of the active layers in the devices is relatively stable after initial relaxation in the first year.
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