Mass production of a 3D non-woven nanofabric with crystalline P3HT nanofibrils for organic solar cells
20 Feb 2013-Energy and Environmental Science (The Royal Society of Chemistry)-Vol. 6, Iss: 3, pp 910-917
TL;DR: In this article, a strategy for the in line mass production of a 3D non-woven nanofabric consisting of crystalline P3HT nanofibrils, created by in situ cooling of the transportation line to feed a P3H solution for a coating tool, was introduced.
Abstract: A strategy for the in line mass production of a three-dimensional (3D) non-woven nanofabric consisting of crystalline P3HT nanofibrils, created by in situ cooling of the transportation line to feed a P3HT solution for a coating tool, was introduced. The required cooling-temperature with respect to the feeding rate for the overall nanofibril creating process and the yield of the nanofibrils in solution with various organic solvents were determined. Considering the influence of a change in the temperature on the status of the precipitated nanofibrils until feeding it into the spray nozzle, the margin of the surviving nanofibrils at a certain temperature was also investigated. To verify the superiority of our strategy and present directions regarding its application to industry, arrays of organic solar cells based on a 3D non-woven nanofabric structure consisting of P3HT nanofibrils were designed and fabricated using our in situ process combined with a spray-coating system. As a result, through the in situ cooling process, a considerable solar energy harvesting efficiency near 4%, which is a state-of-the-art value in a bi-layer-based solar cell, was obtained.
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TL;DR: In this article, the role of thin film morphology on the organic solar cell and organic field effect transistor performance is discussed and the efforts have been taken by the researchers to control the morphology of thin films through the active layer engineering and molecular engineering are summarized.
Abstract: The fast-growing organic electronics field has received the attention of a lot of researchers because of its wide applicability in the consumer electronics, photovoltaics and biotechnology. Since the charge transport, absorption of electromagnetic radiations and exciton migration in the organic semiconductors is direction dependent, it is mandatory to control the morphology and orientation of the active layer with respect to the applications. So, in this review we have briefly discussed the role of thin film morphology on the organic solar cell and organic field-effect transistor performance. And the efforts have been taken by the researchers to control the morphology of thin films through the active layer engineering and molecular engineering are summarized.
5 citations
01 Oct 2018
TL;DR: In contrast to inorganic solar cells, a limitation facing organic solar cells is the inability to produce free charge carriers following light absorption as discussed by the authors, which is a limitation for low-cost and lightweight power generating applications.
Abstract: Constructing solar cells based on organic materials such as conjugated polymers holds great potential for low-cost and lightweight power generating applications. Although organic materials are inexpensive and readily amenable to scale-up, successfully incorporating organic solar cells into the energy sector requires understanding their underlying physics and using this knowledge to increase their efficiency. In contrast to inorganic solar cells, a limitation facing organic solar cells is the inability to produce free charge carriers following light absorption. To overcome this, polymer-based photovoltaics are typically based on a blend of two materials: a conjugated polymer, which acts as the light absorber and electron donor, and an electron acceptor, which is often a fullerene derivative such as phenyl-C61butyric acid methyl ester (PCBM).36,87,136,166 In polymer-fullerene solar cells, light absorption by the semiconducting polymer produces an excited-state electron and leaves
4 citations
TL;DR: In this paper, high-crystallinity poly(3-hexylthiophene) (P3HT) thin films were prepared by aging the precursor solutions, prepared using a good solvent, chloroform, at low temperatures prior to spin-casting.
Abstract: High-crystallinity poly(3-hexylthiophene) (P3HT) thin films were prepared by aging the precursor solutions, prepared using a good solvent, chloroform, at low temperatures prior to spin-casting. Lower solution temperatures significantly improved the molecular ordering in the spin-cast P3HT films and, therefore, the electrical properties of field-effect transistors prepared using these films. Solution cooling enhanced the electrical properties by shifting the P3HT configuration equilibrium away from random coils and toward more ordered aggregates. At room temperature, the P3HT molecules were completely solvated in chloroform and adopted a random coil conformation. Upon cooling, however, the chloroform poorly solvated the P3HT molecules, favoring the formation of ordered P3HT aggregates, which then yielded more highly crystalline molecular ordering in the P3HT thin films produced from the solution.
1 citations
References
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TL;DR: In this paper, the interpenetrating network formed from a phase-segregated mixture of two semiconducting polymers is shown to provide both the spatially distributed interfaces necessary for efficient charge photo-generation, and the means for separately collecting the electrons and holes.
Abstract: THE photovoltaic effect involves the production of electrons and holes in a semiconductor device under illumination, and their subsequent collection at opposite electrodes. In many inorganic semiconductors, photon absorption produces free electrons and holes directly1. But in molecular semiconductors, absorption creates electrona¤-hole pairs (excitons) which are bound at room temperature2, so that charge collection requires their dissociation. Exciton dissociation is known to be efficient at interfaces between materials with different electron affinities and ionization potentials, where the electron is accepted by the material with larger electron affinity and the hole by the material with lower ionization potential3. A two-layer diode structure can thus be used, in which excitons generated in either layer diffuse towards the interface between the layers. However, the exciton diffusion range is typically at least a factor of 10 smaller than the optical absorption depth, thus limiting the efficiency of charge collection3. Here we show that the interpenetrating network formed from a phase-segregated mixture of two semiconducting polymers provides both the spatially distributed interfaces necessary for efficient charge photo-generation, and the means for separately collecting the electrons and holes. Devices using thin films of these polymer mixtures show promise for large-area photodetectors.
3,165 citations
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
TL;DR: In this paper, the self-organization of the polymer in solar cells based on regioregular poly(3-hexylthiophene) (RR-P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) is studied systematically as a function of the spin-coating time.
Abstract: The self-organization of the polymer in solar cells based on regioregular poly(3-hexylthiophene) (RR-P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) is studied systematically as a function of the spin-coating time ts (varied from 20–80 s), which controls the solvent annealing time ta, the time taken by the solvent to dry after the spin-coating process. These blend films are characterized by photoluminescence spectroscopy, UV-vis absorption spectroscopy, atomic force microscopy, and grazing incidence X-ray diffraction (GIXRD) measurements. The results indicate that the π-conjugated structure of RR-P3HT in the films is optimally developed when ta is greater than 1 min (ts ∼ 50 s). For ts < 50 s, both the short-circuit current (JSC) and the power conversion efficiency (PCE) of the corresponding polymer solar cells show a plateau region, whereas for 50 < ts < 55 s, the JSC and PCE values are significantly decreased, suggesting that there is a major change in the ordering of the polymer in this time window. The PCE decreases from 3.6 % for a film with a highly ordered π-conjugated structure of RR-P3HT to 1.2 % for a less-ordered film. GIXRD results confirm the change in the ordering of the polymer. In particular, the incident photon-to-electron conversion efficiency spectrum of the less-ordered solar cell shows a clear loss in both the overall magnitude and the long-wavelength response. The solvent annealing effect is also studied for devices with different concentrations of PCBM (PCBM concentrations ranging from 25 to 67 wt %). Under “solvent annealing” conditions, the polymer is seen to be ordered even at 67 wt % PCBM loading. The open-circuit voltage (VOC) is also affected by the ordering of the polymer and the PCBM loading in the active layer.
1,165 citations
TL;DR: In this paper, the authors provide an overview on the recent development of solution processed organic, inorganic, and hybrid interfacial materials for bulk-heterojunction polymer solar cells.
Abstract: This article provides an overview on the recent development of solution processed organic, inorganic, and hybrid interfacial materials for bulk-heterojunction polymer solar cells. The introduction of proper interfacial materials to optimize the electronic and electrical properties between the interfaces of the light-harvesting active layer and the charge-collecting electrode has become an important criterion to improve the performance of polymer solar cells. The electronic processes at these interfaces play a critical role in determining the efficiency for photon-to-electricity conversion. An ideal interface requires the formation of Ohmic contact with minimum resistance and high charge selectivity to prevent charge carriers from reaching the opposite electrodes. For long-term stability of polymer solar cells, interfaces with matched surface energy are required to prevent interfacial dewetting and delamination. Several classes of interfacial materials including inorganic metal oxides, crosslinkable charge-transporting materials, conjugated polymer electrolytes, self-assembled functional molecules, and graphene-based materials are highlighted and the integration of these interfacial materials with new low bandgap polymers and fullerene derivatives as active materials in different device architectures is also discussed.
995 citations
TL;DR: In this paper, a bilayer of poly(3-hexyl thiophene (P3HT) and poly(6,6]-phenyl-C61-butyric-acid-methyl-ester (PCBM) bulk heterojunction was used for thermal annealing.
Abstract: Developing a better understanding of the evolution of morphology in plastic solar cells is the key to designing new materials and structures that achieve photoconversion efficiencies greater than 10% In the most extensively characterized system, the poly(3-hexyl thiophene) (P3HT):[6,6]-phenyl-C61-butyric-acid-methyl-ester (PCBM) bulk heterojunction, the origins and evolution of the blend morphology during processes such as thermal annealing are not well understood In this work, we use a model system, a bilayer of P3HT and PCBM, to develop a more complete understanding of the miscibility and diffusion of PCBM within P3HT during thermal annealing We find that PCBM aggregates and/or molecular species are miscible and mobile in disordered P3HT, without disrupting the ordered lamellar stacking of P3HT chains The fast diffusion of PCBM into the amorphous regions of P3HT suggests the favorability of mixing in this system, opposing the belief that phase-pure domains form in BHJs due to immiscibility of these two components
625 citations