Thermally Stable, Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology

Ma, Wanli; Yang, Chengwen; Gong, Xiong; Lee, Kwanghee; Heeger, Alan J.

doi:10.1002/adfm.200500211

Cited by 4,508 publications

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“…A substantial improvement in the PCE of P3HT:PCBM based solar cells has been obtained by thermal annealing at around 140 1C, and the favourable influence of annealing on blend film microstructure and solar cell performance is well documented. [50][51][52][53] The mechanism by which current density and PCE increase upon thermal annealing in P3HT:PCBM is not known precisely but it is believed to involve increased optical absorption and improved charge transport, both due to polymer crystallization, as well as improved charge pair separation efficiency, due to optimized phase segregation. Some of the literature is reviewed below.…”

Section: Thermal Annealingmentioning

confidence: 99%

“…60 AFM studies revealed that films cast from more concentrated solutions or solutions with smaller P3HT:PCBM ratios exhibited ''overgrown'' PCBM crystals after high-temperature annealing, leading to degradation of the morphology and poor device performance. 52 A study using differential thermal calorimetry has shown that the P3HT:PCBM binary possesses a eutectic phase behaviour, such that the polymer:fullerene interface area is maximized and the domain size minimized at a blend composition of about 35% PCBM by weight. 61 The higher PCBM content required for maximum efficiency is explained in terms of the need for sufficient PCBM to build up a sufficiently conducting network to achieve balanced charge mobility, in agreement with the ToF measurements cited above.…”

Section: Blend Compositionmentioning

confidence: 99%

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Influence of blend microstructure on bulk heterojunction organic photovoltaic performance

et al. 2011

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This tutorial review discusses the factors influencing blend microstructure and performance in bulk heterojunction organic photovoltaic cells.Please check this proof carefully. Our staff will not read it in detail after you have returned it. Translation errors between word-processor files and typesetting systems can occur so the whole proof needs to be read. Please pay particular attention to: tabulated material; equations; numerical data; figures and graphics; and references. If you have not already indicated the corresponding author(s) please mark their name(s) with an asterisk. Please e-mail a list of corrections or the PDF with electronic notes attached --do not change the text within the PDF file or send a revised manuscript.Please bear in mind that minor layout improvements, e.g. in line breaking, table widths and graphic placement, are routinely applied to the final version.Please note that, in the typefaces we use, an italic vee looks like this: n, and a Greek nu looks like this: n.We will publish articles on the web as soon as possible after receiving your corrections; no late corrections will be made.Please return your final corrections, where possible within 48 hours of receipt, by e-mail to: chemsocrev@rsc.org Reprints-Electronic (PDF) reprints will be provided free of charge to the corresponding author. Enquiries about purchasing paper reprints should be addressed via: http://www.rsc.org/Publishing/ReSourCe/PaperReprints/. Costs for reprints are below: Q3The sentence beginning ''For example it has been shown. . .'' has been altered for clarity, please check that the meaning is correct. Q4The citation to ' Fig. 8(a)' in the sentence beginning 'Grazing-incidence X-ray diffraction (XRD) measurements. . .' has been changed to ' Fig. 10(a)' as the text appears to discuss ' Fig. 10(a)'. Please check that this is correct. Q5The citation to ' Fig. 8(b)' in the sentence beginning 'Upon annealing, P3HT chains begin to crystallize. . .' has been changed to ' Fig The performance of organic photovoltaic devices based upon bulk heterojunction blends of donor and acceptor materials has been shown to be highly dependent on the thin film microstructure. In this tutorial review, we discuss the factors responsible for influencing blend microstructure and how these affect device performance. In particular we discuss how various molecular design approaches can affect the thin film morphology of both the donor and acceptor components, as well as their blend microstructure. We further examine the influence of polymer molecular weight and blend composition upon device performance, and discuss how a variety of processing techniques can be used to control the blend microstructure, leading to improvements in solar cell efficiencies.

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Section: Thermal Annealingmentioning

confidence: 99%

Section: Blend Compositionmentioning

confidence: 99%

Influence of blend microstructure on bulk heterojunction organic photovoltaic performance

et al. 2011

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“…The glancing angle X-ray diffraction (GAXRD) pattern, see Figure 4, of the completed device shows the presence of highly crystalline P3HT, where the peak at 2θ ) 5°corresponds to a P3HT interchain spacing associated with interdigitated alkyl chains. 46,47 Details of the device structure, and hence performance, are dependent on the device fabrication procedure. Consider as an illustration the incident photon to collected electron efficiency (IPCE) of three of the described P3HT/dyesensitized TiO 2 nanotube array devices, see Figure 5, with the P3HT solution (30 mg/mL, prepared using a 3:1 ratio of o-DCB and CB) applied in varying degrees of sample surface wetting as discussed in the preceding paragraph.…”

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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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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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“…Despite the improvements, the reported power conversion efficiencies remain lower than the current record. [31][32][33] Our devices are not fabricated under the exclusion of oxygen, which is known to limit the efficiency to the reported values. For example, domain 5 short circuit current drops by 58% after 10 h of air exposure, which is a common problem for organic thin film solar cells.…”

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Gas Phase Electrodeposition: A Programmable Multimaterial Deposition Method for Combinatorial Nanostructured Device Discovery

2010

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This article reports and applies a recently discovered programmable multimaterial deposition process to the formation and combinatorial improvement of 3D nanostructured devices. The gas-phase deposition process produces charged <5 nm particles of silver, tungsten, and platinum and uses externally biased electrodes to control the material flux and to turn deposition ON/OFF in selected domains. Domains host nanostructured dielectrics to define arrays of electrodynamic 10× nanolenses to further control the flux to form <100 nm resolution deposits. The unique feature of the process is that material type, amount, and sequence can be altered from one domain to the next leading to different types of nanostructures including multimaterial bridges, interconnects, or nanowire arrays with 20 nm positional accuracy. These features enable combinatorial nanostructured materials and device discovery. As a first demonstration, we produce and identify in a combinatorial way 3D nanostructured electrode designs that improve light scattering, absorption, and minority carrier extraction of bulk heterojunction photovoltaic cells. Photovoltaic cells from domains with long and dense nanowire arrays improve the relative power conversion efficiency by 47% when compared to flat domains on the same substrate.

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Thermally Stable, Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology

Cited by 4,508 publications

References 29 publications

Influence of blend microstructure on bulk heterojunction organic photovoltaic performance

Influence of blend microstructure on bulk heterojunction organic photovoltaic performance

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

Gas Phase Electrodeposition: A Programmable Multimaterial Deposition Method for Combinatorial Nanostructured Device Discovery

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Thermally Stable, Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology

Cited by 4,508 publications

References 29 publications

Influence of blend microstructure on bulk heterojunction organic photovoltaic performance

Influence of blend microstructure on bulk heterojunction organic photovoltaic performance

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

Gas Phase Electrodeposition: A Programmable Multimaterial Deposition Method for Combinatorial Nanostructured Device Discovery

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