Dependence of field-effect hole mobility of PPV-based polymer films on the spin-casting solvent

Geens, Wim; Shaheen, Sean E.; Weßling, B.; Brabec, Christoph J.; Poortmans, Jef; Sariciftci, Niyazi Serdar

doi:10.1016/s1566-1199(02)00039-3

Cited by 107 publications

(74 citation statements)

References 12 publications

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“…In one of the first studies using field-effect measurements, an increase of the hole mobility was observed in the PPV:PCBM blends. [71] However, it should be noted that in field-effect transistors the hole mobility of pristine MDMO-PPV is also three orders of magnitude larger compared to the hole mobility in light-emitting diodes or solar cells. [72] This enhancement is a result of the dependence of the mobility on charge carrier density, which is orders of magnitude higher in a transistor than in a solar cell.…”

Section: Charge Transport In Polymer:fullerene Blendsmentioning

confidence: 99%

Device Physics of Polymer:Fullerene Bulk Heterojunction Solar Cells

et al. 2007

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Plastic solar cells bear the potential for large‐scale power generation based on materials that provide the possibility of flexible, lightweight, inexpensive, efficient solar cells. Since the discovery of the photoinduced electron transfer from a conjugated polymer to fullerene molecules, followed by the introduction of the bulk heterojunction (BHJ) concept, this material combination has been extensively studied in organic solar cells, leading to several breakthroughs in efficiency, with a power conversion efficiency approaching 5 %. This article reviews the processes and limitations that govern device operation of polymer:fullerene BHJ solar cells, with respect to the charge‐carrier transport and photogeneration mechanism. The transport of electrons/holes in the blend is a crucial parameter and must be controlled (e.g., by controlling the nanoscale morphology) and enhanced in order to allow fabrication of thicker films to maximize the absorption, without significant recombination losses. Concomitantly, a balanced transport of electrons and holes in the blend is needed to suppress the build‐up of the space–charge that will significantly reduce the power conversion efficiency. Dissociation of electron–hole pairs at the donor/acceptor interface is an important process that limits the charge generation efficiency under normal operation condition. Based on these findings, there is a compromise between charge generation (light absorption) and open‐circuit voltage (VOC) when attempting to reduce the bandgap of the polymer (or fullerene). Therefore, an increase in VOC of polymer:fullerene cells, for example by raising the lowest unoccupied molecular orbital level of the fullerene, will benefit cell performance as both fill factor and short‐circuit current increase simultaneously.

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Section: Charge Transport In Polymer:fullerene Blendsmentioning

confidence: 99%

Device Physics of Polymer:Fullerene Bulk Heterojunction Solar Cells

et al. 2007

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“…[32] A convincing demonstration that liquid crystallinity enhances carrier transport was provided by studying the 9,9-dioctyl polyfluorene PFO as a uniformly aligned nematic glass. [33] An exceptionally large room-temperature hole mobility of 9 10 ±3 cm 2 V ±1 s ±1 was obtained, which compares with a hole mobility of 4 10 ±4 cm 2 V ±1 s ±1 when the same polymer is deposited as an isotropic film.…”

Section: ±1mentioning

confidence: 99%

Liquid Crystals for Charge Transport, Luminescence, and Photonics

O’Neill¹,

2003

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Ordered molecular materials are increasingly used in active electronic and photonic organic devices. In this progress report we discuss whether the self‐assembling properties and supramolecular structures of liquid crystals can be tailored to improve such devices. Recent developments in charge‐transporting and luminescent liquid crystals are discussed in the context of material requirements for organic light‐emitting devices, photovoltaics, and thin film transistors. We identify high carrier mobility, polarized emission, and enhanced output‐coupling as the key advantages of nematic and smectic liquid crystals for electroluminescence. The formation of anisotropic polymer networks gives the added benefits of multilayer capability and photopatternability. The anisotropic transport and high carrier mobilities of columnar liquid crystals make them promising candidates for photovoltaics and transistors. We also outline some of the issues in material design and processing that these applications demand. The photonic properties of chiral liquid crystals and their use as mirror‐less lasers are also discussed.

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“…A possible implication for the charge transport was given as mobility enhancement in an LED device configuration [15] or in a FET configuration. [17] In the context of charge transport it has also been suggested by Rakhmanova and Conwell [2] that in the polymer film there are regions that are better ordered and hence exhibit a narrower (Gaussian) DOS. This morphological effect was shown to affect the field dependence of the mobility.…”

mentioning

confidence: 96%