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ABSTRACT: Novel, nanostructured electrode materials comprising porous ZnO films with aerogel morphology are presented. Almost any substrate including polymers, metals or ceramics can be coated using a method which is suitable for mass-production. The thin, porous films can be prepared from the wet gels via conventional drying, supercritical drying is not necessary. The filigree ZnO network is thermally very stable and exhibits sufficient electrical conductivity for advanced electronic applications. The latter was tested by realizing a highly desired architecture of organic-inorganic hybrid solar cells. After sensitizing of the ZnO with a purely organic squarine dye (SQ2), a nanostructured, interpenetrating 3-D network of the inorganic semiconductor (ZnO) and organic semiconductor (P3HT) was prepared. The solar cell device was tested under illumination with AM 1.5G solar light (100mW/cm2) and exhibited an energy conversion efficiency (ηeff) of 0.69%.
ACS Applied Materials & Interfaces 11/2012; · 4.53 Impact Factor
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ABSTRACT: Imprinted silver nanovoid arrays are investigated via angle-resolved reflectometry to demonstrate their suitability for plasmonic light trapping. Both wavelength- and subwavelength-scale nanovoids are imprinted into standard solar cell architectures to achieve nanostructured metallic electrodes which provide enhanced absorption for improving solar cell performance. The technique is versatile, low-cost and scalable and can be applied to a wide range of organic semiconductors. Absorption features which are independent of incident polarization and weakly dependent on incident angle reveal localized plasmonic modes at the structured interface. Metallic nanostructure-PCPDTBT:PCBM samples demonstrate absorption enhancements of up to 40%. The structured interface provides light trapping, which boosts absorption at wavelengths where the semiconductors absorb poorly.
Nanotechnology 09/2012; 23(38):385202. · 3.98 Impact Factor
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ABSTRACT: Plasmonic light trapping in thin film solar cells is investigated using full-wave electromagnetic simulations. Light absorption in the semiconductor layer with three standard plasmonic solar cell geometries is compared to absorption in a flat layer. We identify near-field absorption enhancement due to the excitation of localized surface plasmons but find that it is not necessary for strong light trapping in these configurations: significant enhancements are also found if the real metal is replaced by a perfect conductor, where scattering is the only available enhancement mechanism. The absorption in a 60 nm thick organic semiconductor film is found to be enhanced by up to 19% using dispersed silver nanoparticles, and up to 13% using a nanostructured electrode. External in-scattering nanoparticles strongly limit semiconductor absorption via back-reflection.
Optics Express 03/2012; 20 Suppl 2:A177-89. · 3.59 Impact Factor
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Laser Physics Review 06/2011; 1(5):861 - 869.
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ABSTRACT: This Progress Report highlights recent developments in nanostructured organic and hybrid solar cells. The authors discuss novel approaches to control the film morphology in fully organic solar cells and the design of nanostructured hybrid solar cells. The motivation and recent results concerning fabrication and effects on device physics are emphasized. The aim of this review is not to give a summary of all recent results in organic and hybrid solar cells, but rather to focus on the fabrication, device physics, and light trapping properties of nanostructured organic and hybrid devices.
Advanced Materials 04/2011; 23(16):1810-28. · 13.88 Impact Factor
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Advanced Functional Materials 12/2010; 21(3):573 - 582. · 10.18 Impact Factor
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Advanced Materials 09/2010; 22(35):E254-8. · 13.88 Impact Factor
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Materials Today. 01/2007; 10(5):40-48.
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ABSTRACT: The method of spray-depositing PEDOT:PSS allows the fabrication of thin films with controlled thickness on polymer layers. PEDOT:PSS is used in inverted ITO/TiO2/P3HT:PCBM/PEDOT:PSS/Ag solar cells to optimize the work function of the hole-collecting electrode. The interlayer is also found to protect the organic layer during metal top deposition and improve the contact between P3HT–PCBM and the Ag electrode, which is confirmed using two different metal-deposition techniques; thermal evaporation and sputtering. Cells with PEDOT:PSS show full VOC and efficiency immediately after fabrication, whereas devices without PEDOT:PSS exhibit low performance in the beginning and improve significantly during the first 10 days after production. Devices are long-term stable if stored in the dark and in ambient air and show no significant performance decrease after 80 days. No inert nitrogen atmosphere is needed for any fabrication step, thus reducing the potential production costs since no glove box has to be used.
Solar Energy Materials and Solar Cells.
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ABSTRACT: We consider the suitability of metallic nanovoid arrays for confining incident light and enhancing absorption in an adjacent absorbing material, such as an organic semiconductor. Such nanostructures can facilitate strong coupling of incident light into plasmonic modes localized at the surface of the metal. We investigate this system both experimentally and by performing numerical calculations. To fabricate the samples, we employ a novel imprinting technique to obtain large-area, highly ordered metallic nanovoid arrays. Strong overall absorption enhancements are measured for nanostructured samples compared to planar samples for interfaces between silver and a common organic semiconductor, phenyl-C61-butyric acid methyl ester. Full-wave, three-dimensional finite element method simulations are employed to investigate the nature of this light trapping, and very good agreement is observed between experimental and simulated absorption spectra. The simulations reveal highly localized surface modes and indicate that the majority of the additional absorption occurs within the organic semiconductor.
Phys. Rev. B. 85(3).
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ABSTRACT: Discotic materials have attracted remarkable interest for application in organic solar cells. We analyze a series of phenyl-substituted hexa-peri-hexabenzocoronenes (HBCs) with residue modifications blended with perylenediimide (PDI) as donor material. The effect of differing alkyl chain lengths of 6, 8, 12 and 16 carbon atoms, introduction of a triple bond linker between HBC core and residual phenyl group and a swallow tailed dialkylphenyl chain on the device performance is investigated. Detailed insight to device physics and morphology is gained by analysis of photoluminescence quenching, transient photovoltage and photocurrent decay experiments and atomic force microscopy. Complementary the investigations explain why using short alkyl side chains higher currents and consequently increased device performance can be achieved. We report an external quantum efficiency of over 27% for devices based on discotic molecules. In this work the molecular assembly and its impact on performance in photovoltaic devices is studied. The study also reveals pathways to further increase the quantum yield of small molecule organic solar cells.
Solar Energy Materials and Solar Cells.
