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J Joachim Loos

Bio: J Joachim Loos is an academic researcher from Energy Research Centre of the Netherlands. The author has contributed to research in topics: Polymer solar cell & Heterojunction. The author has an hindex of 3, co-authored 4 publications receiving 2194 citations.

Papers
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Journal ArticleDOI
TL;DR: Both the improved crystalline nature of films and increased but controlled demixing between the two constitutes therein after annealing explains the considerable increase of the power conversion efficiency observed in these devices.
Abstract: Transmission electron microscopy and electron diffraction are used to study the changes in morphology of composite films of poly(3-hexylthiophene) (P3HT) and a methanofullerene derivative (PCBM) in bulk heterojunction solar cells. Thermal annealing produces and stabilizes a nanoscale interpenetrating network with crystalline order for both components. P3HT forms long, thin conducting nanowires in a rather homogeneous, nanocrystalline PCBM film. Both the improved crystalline nature of films and increased but controlled demixing between the two constitutes therein after annealing explains the considerable increase of the power conversion efficiency observed in these devices.

1,552 citations

Journal ArticleDOI
TL;DR: The electro-optical properties of thin films of electron donor-acceptor blends of a fluorene copolymer and a fullerene derivative were studied and it is shown that in these films nanocrystalline PCBM clusters are formed at high PCBM content.
Abstract: The electro-optical properties of thin films of electron donor−acceptor blends of a fluorene copolymer (PF10TBT) and a fullerene derivative (PCBM) were studied. Transmission electron microscopy shows that in these films nanocrystalline PCBM clusters are formed at high PCBM content. For all concentrations, a charge transfer (CT) transition is observed with absorption spectroscopy, photoluminescence, and electroluminescence. The CT emission is used as a probe to investigate the dissociation of CT excited states at the donor−acceptor interface in photovoltaic devices, as a function of an applied external electric field and PCBM concentration. We find that the maximum of the CT emission shifts to lower energy and decreases in intensity with higher PCBM content. We explain the red shift of the emission and the lowering of the open-circuit voltage (V OC) of photovoltaic devices prepared from these blends with the higher relative permittivity of PCBM (er = 4.0) compared to that of the polymer (er = 3.4), stabili...

566 citations

Journal ArticleDOI
TL;DR: In this paper, the photovoltaic properties of solution-processed semiconducting polymer blends have been studied and it is demonstrated that photoinduced charge transfer occurs in binary mixtures of poly[2-methoxy-5-(3, 7-dimethyl octyloxy)-1, 4-phenylenevinylene] (MDMO-PPV) and poly-[oxa-1,4-,1,phenylene-(1-cyano-1-2-vinylene)-(2-nylon)-1.4-,phenylene)-1
Abstract: Photovoltaic properties of solution-processed semiconducting polymer blends have been studied. It is demonstrated that photoinduced charge transfer occurs in binary mixtures of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and poly-[oxa-1,4-phenylene-(1-cyano-1,2-vinylene)-(2-methoxy-5-(3, 7-dimethyloctyloxy)-1,4-phenylene)-1,2-(2-cyanovinylene)-1,4-phenylene] (PCNEPV). Further, it is shown that the photovoltaic performance is improved by a thermal treatment which alters the morphology of the photoactive layer. The temperature necessary to achieve the enhanced performance is related to transition temperatures of the pure polymers. Device optimization yields solar cells with a power conversion efficiency of 0.75% under standard test conditions (AM 1.5, 1000 W/m2).

121 citations

Proceedings ArticleDOI
06 Feb 2004
TL;DR: In this paper, the authors used poly(2-methoxy-5-(3,7-dimethyl octyloxy)-1,4-phenylene-vinylene) (MDMO-PPV) as donor and poly(cyanoetherphenylenevinylene), (PCNEPV) derivatives as acceptor material.
Abstract: Polymer bulk hetero junction solar cells were made from poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene-vinylene) (MDMO-PPV) as donor and poly(cyanoetherphenylenevinylene) (PCNEPV) derivatives as acceptor material. In this paper we start out with discussing the synthesis of the materials. Subsequently, the main issues concerning the devices are treated. Annealing the devices yielded devices with encouraging efficiencies of 0.5% (1 sun, 100mW/cm2), as calculated from the maximum power points (MPP). AFM studies revealed that this anneal step improves especially the interface of the active layer with the under laying PEDOT:PSS, although mobility and morphology changes can not be ruled out. Lowering the molecular weight (Mw) of the MDMO-PPV gave a slight improvement of the device performance. Decreasing the Mw of the acceptor material, MDMO-PCNEPV (PCNEPV derivative with the same side chains as MDMO-PPV) and optimizing the layer thickness led to a device with an efficiency of 0.65%. Finally we looked into the influence of the nature of the side chains on the acceptor polymer. The results suggest that the closer the resemblance between donor and acceptor is the better the device performance.

3 citations


Cited by
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Journal ArticleDOI
TL;DR: This review gives a general introduction to the materials, production techniques, working principles, critical parameters, and stability of the organic solar cells, and discusses the alternative approaches such as polymer/polymer solar cells and organic/inorganic hybrid solar cells.
Abstract: The need to develop inexpensive renewable energy sources stimulates scientific research for efficient, low-cost photovoltaic devices.1 The organic, polymer-based photovoltaic elements have introduced at least the potential of obtaining cheap and easy methods to produce energy from light.2 The possibility of chemically manipulating the material properties of polymers (plastics) combined with a variety of easy and cheap processing techniques has made polymer-based materials present in almost every aspect of modern society.3 Organic semiconductors have several advantages: (a) lowcost synthesis, and (b) easy manufacture of thin film devices by vacuum evaporation/sublimation or solution cast or printing technologies. Furthermore, organic semiconductor thin films may show high absorption coefficients4 exceeding 105 cm-1, which makes them good chromophores for optoelectronic applications. The electronic band gap of organic semiconductors can be engineered by chemical synthesis for simple color changing of light emitting diodes (LEDs).5 Charge carrier mobilities as high as 10 cm2/V‚s6 made them competitive with amorphous silicon.7 This review is organized as follows. In the first part, we will give a general introduction to the materials, production techniques, working principles, critical parameters, and stability of the organic solar cells. In the second part, we will focus on conjugated polymer/fullerene bulk heterojunction solar cells, mainly on polyphenylenevinylene (PPV) derivatives/(1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61) (PCBM) fullerene derivatives and poly(3-hexylthiophene) (P3HT)/PCBM systems. In the third part, we will discuss the alternative approaches such as polymer/polymer solar cells and organic/inorganic hybrid solar cells. In the fourth part, we will suggest possible routes for further improvements and finish with some conclusions. The different papers mentioned in the text have been chosen for didactical purposes and cannot reflect the chronology of the research field nor have a claim of completeness. The further interested reader is referred to the vast amount of quality papers published in this field during the past decade.

6,059 citations

Journal ArticleDOI
TL;DR: By applying specific fabrication conditions summarized in the Experimental section and post-production annealing at 150°C, polymer solar cells with power-conversion efficiency approaching 5% were demonstrated.
Abstract: By applying the specific fabrication conditions summarized in the Experimental section and post-production annealing at 150 °C, polymer solar cells with power-conversion efficiency approaching 5 % are demonstrated. These devices exhibit remarkable thermal stability. We attribute the improved performance to changes in the bulk heterojunction material induced by thermal annealing. The improved nanoscale morphology, the increased crystallinity of the semiconducting polymer, and the improved contact to the electron-collecting electrode facilitate charge generation, charge transport to, and charge collection at the electrodes, thereby enhancing the device efficiency by lowering the series resistance of the polymer solar cells.

4,513 citations

Journal ArticleDOI
TL;DR: Polymer-based organic photovoltaic systems hold the promise for a cost-effective, lightweight solar energy conversion platform, which could benefit from simple solution processing of the active layer.
Abstract: Fossil fuel alternatives, such as solar energy, are moving to the forefront in a variety of research fields. Polymer-based organic photovoltaic systems hold the promise for a cost-effective, lightweight solar energy conversion platform, which could benefit from simple solution processing of the active layer. The function of such excitonic solar cells is based on photoinduced electron transfer from a donor to an acceptor. Fullerenes have become the ubiquitous acceptors because of their high electron affinity and ability to transport charge effectively. The most effective solar cells have been made from bicontinuous polymer–fullerene composites, or so-called bulk heterojunctions. The best solar cells currently achieve an efficiency of about 5 %, thus significant advances in the fundamental understanding of the complex interplay between the active layer morphology and electronic properties are required if this technology is to find viable application.

3,911 citations

Journal ArticleDOI
TL;DR: In this article, a review summarizes recent progress in the development of polymer solar cells and provides a synopsis of major achievements in the field over the past few years, while potential future developments and the applications of this technology are also briefly discussed.
Abstract: This Review summarizes recent progress in the development of polymer solar cells. It covers the scientific origins and basic properties of polymer solar cell technology, material requirements and device operation mechanisms, while also providing a synopsis of major achievements in the field over the past few years. Potential future developments and the applications of this technology are also briefly discussed.

3,832 citations

Journal ArticleDOI
TL;DR: In this paper, the entire process leading to polymer solar cells is broken down into the individual steps and the available techniques and materials for each step are described with focus on the particular advantages and disadvantages associated with each case.

3,090 citations