Conjugated Polymer Photovoltaic Cells

Coakley, Kevin M.; McGehee, Michael D.

doi:10.1021/cm049654n

Cited by 2,100 publications

(1,711 citation statements)

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“…There is a small red shift of 9 nm in the peak position for SQ-1 suggesting J-type aggregation, which can further extend the photon absorption into the NIR region. P3HT coverage of the TiO 2 nanotube arrays shows no shift in the absorption peak position compared to that of neat P3HT films, 34 indicating a high degree of π-π stacking of the polymer chains within the nanotubes. The spectral properties of the SQ-1 dye in ethanol solution and cyclic voltammetry determined electrochemical properties of the sensitizers upon the TiO 2 nanotube arrays are summarized in Table 1.…”

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confidence: 95%

Visible to Near-Infrared Light Harvesting in TiO₂ Nanotube Array−P3HT Based Heterojunction Solar Cells

et al. 2009

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The development of high-efficiency solid-state excitonic photovoltaic solar cells compatible with solution processing techniques is a research area of intense interest, with the poor optical harvesting in the red and near-IR (NIR) portion of the solar spectrum a significant limitation to device performance. Herein we present a solid-state solar cell design, consisting of TiO 2 nanotube arrays vertically oriented from the FTOcoated glass substrate, sensitized with unsymmetrical squaraine dye (SQ-1) that absorbs in the red and NIR portion of solar spectrum, and which are uniformly infiltrated with p-type regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) that absorbs higher energy photons. Our solidstate solar cells exhibit broad, near-UV to NIR, spectral response with external quantum yields of up to 65%. Under UV filtered AM 1.5G of 90 mW/cm 2 intensity we achieve typical device photoconversion efficiencies of 3.2%, with champion device efficiencies of 3.8%.The best performing bulk heterojunction solar cells (η ∼ 6%) employ an optimized blend of a polymeric donor and a fullerene acceptor. 1,2 The fullerene acceptor absorbs very little light and is primarily used in blends to provide an efficient interface for exciton dissociation. Various efforts toward efficiency improvement in these devices are directed toward the development of low band gap polymers to absorb a broad swathe of the solar spectrum, 3-6 lowering the molecular energy levels of the semiconducting polymer to enhance the open circuit voltage of the organic solar cells, 1,7 and the control of the blended film morphology for enhanced exciton harvesting. [8][9][10][11][12] In the best performing solid-state dyesensitized solar cells (SS-DSSCs), η ∼ 5%, the only photon absorber is a dye, while the electron and hole transport functions are performed, respectively, by a disordered nanoparticulate TiO 2 network and a transparent small molecule spiro-OMeTAD. [13][14][15][16] To achieve higher efficiency devices, research efforts have focused on improved porefilling by the hole transporter, the use of higher mobility hole transporters and the synthesis of dyes with a broader and more-intense absorption spectrum.Red/NIR radiation (650-1000 nm) accounts for approximately 33% of the solar energy arriving at the surface of the Earth, while UV-visible radiation (350-650 nm) accounts for about 40%. Hence a key issue toward achieving higher efficiency organic solar cells is in the development of red and NIR absorbing molecules to utilize more of the solar spectrum. As an approach for efficiently utilizing visible to NIR solar radiation, herein we describe an inorganic-organic hybrid solar cell, see Figure 1a, where electron transporting TiO 2 nanotube arrays, sensitized with red and NIR light absorbing organic dye, are used in combination with hole transporting and visible light absorbing regioregular P3HT. [17][18][19] It should be noted that this low band gap organic dye should not block transmission of the high-energy photons of near-UV-visible range pa...

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Visible to Near-Infrared Light Harvesting in TiO₂ Nanotube Array−P3HT Based Heterojunction Solar Cells

et al. 2009

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“…Current research has focused on controlling the morphology of donor-acceptor mixtures or block copolymers, attempting to balance charge transport and increase light absorption. 4,[8][9][10][11][12] A maximum efficiency of 8.3% was obtained for a single active layer BHJ device. 13 Three different types of morphologies have been used in the active layer of OPVs, including bilayers, BHJs and ordered BHJs, which are schematized in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

On the morphology of polymer‐based photovoltaics

Liu

Jung

et al. 2012

J Polym Sci B Polym Phys

309

248

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We review the morphologies of polymer-based solar cells and the parameters that govern the evolution of the morphologies and describe different approaches to achieve the optimum morphology for a BHJ OPV. While there are some distinct differences, there are also some commonalities. It is evident that morphology and the control of the morphology are important for device performance and, by controlling the thermodynamics, in particular, the interactions of the components, and by controlling kinetic parameters, like the rate of solvent evaporation, crystallization and phase separation, optimized morphologies for a given system can be achieved. While much research has focused on P3HT, it is evident that a clearer understanding of the morphology and the evolution of the morphology in low bad gap polymer systems will increase the efficiency further. While current OPVs are on the verge of breaking the 10% barrier, manipulating and controlling the morphology will still be key for device optimization and, equally important, for the fabrication of these devices in an industrial setting.

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“…Semiconductor films with a dense array of pores at the 10-50 nm length scale are attractive for photovoltaics, [1][2][3][4] photocatalytics, 5,6 and sensing applications. 7 For these applications, it is desirable to pattern semiconductors in a relatively simple and cheap process.…”

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Nanostructuring Titania by Embossing with Polymer Molds Made from Anodic Alumina Templates

2005

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We demonstrate a method for embossing titania sol−gel precursor with poly(methyl methacrylate) (PMMA) molds to make thin films of titania that have dense arrays of 35−65 nm diameter pores, whose features are 1 order of magnitude smaller than those previously demonstrated for sol−gel molding. We show that the high modulus of PMMA is necessary to preserve small features with high aspect ratios on the mold for nanopatterning. The molds are prepared by thermally infiltrating PMMA into anodic alumina templates, whose pore dimensions and depths are adjustable by varying anodization conditions. The difficulties associated with mold release from a master are avoided by wet etching the template. These titania films, and others made with other semiconductors, could be useful for photovoltaic, photocatalytic, and sensing applications where nanostructuring of surfaces with controlled dimensions are essential.Nanostructured semiconductor materials have drawn a lot of attention because they exhibit interesting optical, electronic, and catalytic properties. Semiconductor films with a dense array of pores at the 10-50 nm length scale are attractive for photovoltaics, 1-4 photocatalytics, 5,6 and sensing applications. 7 For these applications, it is desirable to pattern semiconductors in a relatively simple and cheap process. Although soft lithography 8 and nanoimprint lithography 9 are promising ways to nanopattern materials, they both have limitations and may not be suitable for patterning certain materials and specifications. Soft lithography, which usually utilizes elastomer poly(dimethylsiloxane) (PDMS) molds, has been extensively used to pattern photoresists, biological macromolecules, and semiconducting polymers. 8,10 The resolution achievable with PDMS however has often been limited to >100 nm due to its relatively low compression modulus of ∼2 MPa. 11 The use of a harder version of PDMS (h-PDMS) with a compression modulus of ∼9 MPa has increased the resolution to about 50 nm, 11,12 but only for features that are not densely spaced together and of high aspect ratio. This points to the need for an even harder mold as patterning is pushed toward increasingly smaller scale. Nanoimprint lithography, which has formidable resolution approaching 5 nm, 13 uses a hard Si or SiO 2 mold to achieve high aspect ratio features. Nanoimprinted materials include photoresists, polymers, silicon, and sol-gel materials, 9,14-16 but some other materials cannot be patterned by nanoimprint lithography because the mold adheres to the film and cannot be removed. For instance, nanostructuring of sol-gel inorganics potentially useful in many low cost applications can be very challenging with either soft lithography or nanoimprint lithography. Here, we demonstrate molding of solgel precursors to make nanostructured metal oxide films, whose features are 1 order of magnitude smaller than those previously demonstrated for sol-gel molding. 15,17 We show that embossing with a hard polymer mold can be an attractive alternative to pattern nanoporo...

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Conjugated Polymer Photovoltaic Cells

Cited by 2,100 publications

References 88 publications

Visible to Near-Infrared Light Harvesting in TiO₂ Nanotube Array−P3HT Based Heterojunction Solar Cells

Visible to Near-Infrared Light Harvesting in TiO₂ Nanotube Array−P3HT Based Heterojunction Solar Cells

On the morphology of polymer‐based photovoltaics

Nanostructuring Titania by Embossing with Polymer Molds Made from Anodic Alumina Templates

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Conjugated Polymer Photovoltaic Cells

Cited by 2,100 publications

References 88 publications

Visible to Near-Infrared Light Harvesting in TiO2 Nanotube Array−P3HT Based Heterojunction Solar Cells

Visible to Near-Infrared Light Harvesting in TiO2 Nanotube Array−P3HT Based Heterojunction Solar Cells

On the morphology of polymer‐based photovoltaics

Nanostructuring Titania by Embossing with Polymer Molds Made from Anodic Alumina Templates

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Visible to Near-Infrared Light Harvesting in TiO₂ Nanotube Array−P3HT Based Heterojunction Solar Cells

Visible to Near-Infrared Light Harvesting in TiO₂ Nanotube Array−P3HT Based Heterojunction Solar Cells