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We have studied the effect of silicon nanocrystals (SiNCs) as a third component on performance of organic bulk heterojunction solar cells composed of poly[2-methoxy,5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend film. By adding suitable amounts of SiNCs into MEH-PPV:PCBM blend, the device performance such as external quantum efficiency, short circuit current density ( JSC), and power conversion efficiency (PCE) improved. Incorporation of 2.5% SiNCs in the blend led to 13.6% improvement of JSC, which in turn resulted in 18% improvement of PCE up to 2.28%. The improved performance was mainly due to the improvements both in the charge generation from the interface of MEH-PPV/SiNCs and the charge collection at the cathode. [ABSTRACT FROM AUTHOR]

Abstract: All-polymer bulk-heterojunction photovoltaic cells based on poly(N-vinyl carbazole) and poly(9,9-dioctylfluorene-co-benzothiadiazole) co-casting films are investigated. One of the highest reported open-circuit voltage among the all-polymer solar cells is obtained due to the large energy offset between the highest occupied molecular orbital of the donor and the lowest unoccupied molecular orbital of the acceptor. Atomic force microscopy and photoluminescence study of the active layer with varied blending ratios and annealing temperatures reveals a phase controlled working mechanism, in which the charge generation efficiency is proved to be the main limiting factor of this material system. The incident photon-to-current conversion efficiency measurement shows a unique “double peak” phenomenon with increase in the annealing temperature, indicative of asynchronous chain movement between the two polymers due to their relatively large difference in glass transition temperature. Such a phase behavior might have potential value in further optimization of film morphology towards higher device performance. [ABSTRACT FROM AUTHOR]

We report that a very thin n-type Sb2O3 anode buffer layer in copper phthalocyanine (CuPc)/fullerene (C60) organic solar cells (OSCs) increases the power conversion efficiency by a factor of ∼34%. The enhancement is mostly attributed to the preferred orientation of CuPc layer and the increased contact area of CuPc/C60 interface, induced by the Sb2O3 layer rather than commonly regarded energy level alignment achieved by other metal oxides such as MoO3. Our study provides an insight to understand effect of the metal oxide buffer layers on the morphological influence in organic solar cells. [ABSTRACT FROM AUTHOR]

Abstract: We fabricated polymer bulk heterojunction solar cells with blends of poly (2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) by using CsF as an interlayer. Under illumination, the device with Al/CsF cathode exhibited a higher energy conversion efficiency compared to the Al/LiF cathode. The performance improvement with the Al/CsF cathode comes from the lower series resistance, which is almost constant (~6Ωcm2) for all the CsF layer thicknesses included in the present study. The mechanism responsible for this phenomenon is attributed to the dissociation of CsF upon Al deposition to liberate Cs with a low work function, which reduces the interface resistance of the active layer/cathode and enhances the interior electric field for more efficient charge transport in the device. [Copyright &y& Elsevier]

Abstract: The effect of n-type phthalocyanine tin (IV) dichloride (SnCl2Pc) as cathode interfacial layer on the performance of poly[2-methoxy,5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction solar cells (ITO/PEDOT:PSS/MEH-PPV:PCBM/SnCl2Pc/LiF/Al) is investigated. Our results show that the integration of SnCl2Pc into the solar cell not only enhances the exciton dissociation efficiency due to the formation of additional MEH-PPV/SnCl2Pc exciton dissociation junction, but also improves the electron transport and collection due to the step-like electron injection barrier to cathode caused by SnCl2Pc interlayer. The incorporation of 6nm thick SnCl2Pc interlayer leads to 15.7% improvement of the short circuit current density (J SC ), which in turn results in 15.2% improvement of power conversion efficiency (η) up to 2.49%. The results suggest that the employment of an n-type organic semiconductor like SnCl2Pc as an interlayer is a promising strategy to improve the device performance of polymer solar cells. [Copyright &y& Elsevier]

Abstract: This paper reported the fabrication of CdS nanorod arrays on transparent conductive tin-doped In2O3 (ITO) glass substrate by combining electrodeposition and hydrothermal processes. One thin layer of CdS particles on substrates was prepared by electrodeposition as seeds, upon which well-aligned nanorod arrays were hydrothermally grown in large scale. The morphology, structure and phase composition of CdS nanorod arrays were examined by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), and high-resolution TEM. The optical absorption spectra and the temperature-dependent photoluminescence of CdS nanorod arrays were also studied. An organic/inorganic hybrid solar cell prototype device was fabricated based on the as-prepared CdS nanoarrays grown on the transparent ITO electrode (ITO/CdS arrays/poly[2-methoxy-5-(20-ethylhexyloxy)-1,4-phenylene-vinylene]/Au). The power conversion efficiency was 0.06%, showing an obvious photovoltaic effect. [Copyright &y& Elsevier]

Abstract: Three new diketopyrrolopyrrole (DPP)-containing poly(phenylene vinylene)s varying at N-alkyl or 3,6-aryl substituents in DPP units, abbreviated as C6DPPDHPV, C6DTDPPDHPV, and C62DTDPPDHPV, were designed to comparatively study the structural effects on their photophysical, electrochemical properties, molecular organization and photovoltaic properties. The polymers exhibited remarkably broad UV–vis absorption spectra covering a major part of the wavelength range of visible light in the solar spectrum, and small bandgaps between 1.4 and 1.9eV. X-ray diffraction and cyclic voltammetry measurements revealed that N-alkyl and 3,6-aryl in DPP unit played a key role in tuning their molecular organization as well as electrochemical behavior. The bulk heterojunction photovoltaic devices employing the three polymers as electron donors, together with PC61BM as electron acceptor, were examined. C6DPPDHPV based device showed the highest energy conversion efficiency of 0.72%. Lower hole mobilities and relatively higher HOMO energy levels may be responsible for inferior performance of C6DTDPPDHPV and C62DTDPPDHPV-based devices. Moreover, the C6DPPDHPV was preliminarily evaluated as active material in organic thin film transistor. [ABSTRACT FROM AUTHOR]