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Hou X, Coker JF, Yan J, Shi X, Azzouzi M, Eisner FD, McGettrick JD, Tuladhar SM, Abrahams I, Frost JM, Li Z, Dennis TJS, Nelson J. Structure-Property Relationships for the Electronic Applications of Bis-Adduct Isomers of Phenyl-C 61 Butyric Acid Methyl Ester. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2024; 36:425-438. [PMID: 38222935 PMCID: PMC10782444 DOI: 10.1021/acs.chemmater.3c02353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 11/26/2023] [Accepted: 11/27/2023] [Indexed: 01/16/2024]
Abstract
Higher adducts of a fullerene, such as the bis-adduct of PCBM (bis-PCBM), can be used to achieve shallower molecular orbital energy levels than, for example, PCBM or C60. Substituting the bis-adduct for the parent fullerene is useful to increase the open-circuit voltage of organic solar cells or achieve better energy alignment as electron transport layers in, for example, perovskite solar cells. However, bis-PCBM is usually synthesized as a mixture of structural isomers, which can lead to both energetic and morphological disorder, negatively affecting device performance. Here, we present a comprehensive study on the molecular properties of 19 pure bis-isomers of PCBM using a variety of characterization methods, including ultraviolet photoelectron spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, single crystal structure, and (time-dependent) density functional theory calculation. We find that the lowest unoccupied molecular orbital of such bis-isomers can be tuned to be up to 170 meV shallower than PCBM and up to 100 meV shallower than the mixture of unseparated isomers. The isolated bis-isomers also show an electron mobility in organic field-effect transistors of up to 4.5 × 10-2 cm2/(V s), which is an order of magnitude higher than that of the mixture of bis-isomers. These properties enable the fabrication of the highest performing bis-PCBM organic solar cell to date, with the best device showing a power conversion efficiency of 7.2%. Interestingly, we find that the crystallinity of bis-isomers correlates negatively with electron mobility and organic solar cell device performance, which we relate to their molecular symmetry, with a lower symmetry leading to more amorphous bis-isomers, less energetic disorder, and higher dimensional electron transport. This work demonstrates the potential of side chain engineering for optimizing the performance of fullerene-based organic electronic devices.
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Affiliation(s)
- Xueyan Hou
- Department
of Physics, Imperial College London, London SW7 2AZ, U.K.
- School
of Physical and Chemical Sciences, Queen
Mary University of London, London E1 4NS, U.K.
| | - Jack F. Coker
- Department
of Physics, Imperial College London, London SW7 2AZ, U.K.
| | - Jun Yan
- Department
of Physics, Imperial College London, London SW7 2AZ, U.K.
- School
of Science and Engineering, The Chinese
University of Hong Kong, Shenzhen, Guangdong Province 518172, P. R. China
| | - Xingyuan Shi
- Department
of Physics, Imperial College London, London SW7 2AZ, U.K.
| | - Mohammed Azzouzi
- Department
of Physics, Imperial College London, London SW7 2AZ, U.K.
| | - Flurin D. Eisner
- Department
of Physics, Imperial College London, London SW7 2AZ, U.K.
| | | | | | - Isaac Abrahams
- School
of Physical and Chemical Sciences, Queen
Mary University of London, London E1 4NS, U.K.
| | - Jarvist M. Frost
- Department
of Physics, Imperial College London, London SW7 2AZ, U.K.
| | - Zhe Li
- School
of Engineering and Materials Sciences, Queen
Mary University of London, London E1 4NS, U.K.
| | - T. John S. Dennis
- Department
of Chemistry, Xi’an Jiaotong-Liverpool
University, Suzhou 215123, China
| | - Jenny Nelson
- Department
of Physics, Imperial College London, London SW7 2AZ, U.K.
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Hou X, Duan X, Liang M, Wang Z, Yan D. Application of Bis-Adducts of Phenyl-C 61 Butyric Acid Methyl Ester in Promoting the Open-Circuit Voltage of Indoor Organic Photovoltaics. MATERIALS (BASEL, SWITZERLAND) 2023; 16:2613. [PMID: 37048908 PMCID: PMC10095513 DOI: 10.3390/ma16072613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 03/20/2023] [Accepted: 03/23/2023] [Indexed: 06/19/2023]
Abstract
Fullerene-based indoor OPVs, particularly phenyl-C61 butyric acid methyl ester (PCBM), has been regarded as a prospective harvesting indoor light energy source to drive low-power consumption electronic devices such as sensors and IoTs. Due to the low tunability of its inherently spherical structure, the performance of the fullerene-based indoor OPVs seem to hit a bottleneck compared with the non-fullerene materials. Here, we explore the potential application of fullerene derivative bis-PCBM in indoor OPVs, which owns a higher the lowest unoccupied molecular orbital (LUMO) level than PCBM. The results show that when blended with PCDTBT, bis-PCBM devices yield a high VOC of up to 1.05 V and 0.9 V under AM 1.5G illumination and 1000 lx indoor light, compared with the corresponding values of 0.93 V and 0.79 V for PCBM devices. Nevertheless, the disorders in bis-PCBM suppress the JSC and FF and, therefore, result in a lower efficiency compared to PCBM devices. However, the efficiency and stability differences between the two kinds of cells were much reduced under indoor light conditions. After further optimization of the material composition and fabrication process, bis-PCBM could be an alternative to PCBM, offering great potential for indoor OPV with high performance.
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Affiliation(s)
- Xueyan Hou
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Xiaohan Duan
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Mengnan Liang
- Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, School of Physics and Optoelectronic Engineering, Foshan University, Foshan 528225, China
| | - Zixuan Wang
- School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110819, China
| | - Dong Yan
- Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, School of Physics and Optoelectronic Engineering, Foshan University, Foshan 528225, China
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3
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Scarongella M, De Jonghe-Risse J, Buchaca-Domingo E, Causa' M, Fei Z, Heeney M, Moser JE, Stingelin N, Banerji N. A close look at charge generation in polymer:fullerene blends with microstructure control. J Am Chem Soc 2015; 137:2908-18. [PMID: 25650696 DOI: 10.1021/ja510032x] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We reveal some of the key mechanisms during charge generation in polymer:fullerene blends exploiting our well-defined understanding of the microstructures obtained in pBTTT:PCBM systems via processing with fatty acid methyl ester additives. Based on ultrafast transient absorption, electro-absorption, and fluorescence up-conversion spectroscopy, we find that exciton diffusion through relatively phase-pure polymer or fullerene domains limits the rate of electron and hole transfer, while prompt charge separation occurs in regions where the polymer and fullerene are molecularly intermixed (such as the co-crystal phase where fullerenes intercalate between polymer chains in pBTTT:PCBM). We moreover confirm the importance of neat domains, which are essential to prevent geminate recombination of bound electron-hole pairs. Most interestingly, using an electro-absorption (Stark effect) signature, we directly visualize the migration of holes from intermixed to neat regions, which occurs on the subpicosecond time scale. This ultrafast transport is likely sustained by high local mobility (possibly along chains extending from the co-crystal phase to neat regions) and by an energy cascade driving the holes toward the neat domains.
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Affiliation(s)
- Mariateresa Scarongella
- Institute of Chemical Sciences & Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL) , SB ISIC GR-MO, Station 6, CH-1015 Lausanne, Switzerland
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4
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Wang Y, Benten H, Ohara S, Kawamura D, Ohkita H, Ito S. Measurement of exciton diffusion in a well-defined donor/acceptor heterojunction based on a conjugated polymer and cross-linked fullerene derivative. ACS APPLIED MATERIALS & INTERFACES 2014; 6:14108-14115. [PMID: 25051391 DOI: 10.1021/am503434p] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We designed a well-defined donor/acceptor heterojunction for measuring exciton diffusion lengths in conjugated polymers. To obtain an insoluble electron acceptor layer, a new cross-linkable fullerene derivative (bis-PCBVB) was synthesized by functionalizing [6,6]-diphenyl-C62-bis(butyric acid methyl ester) (bis-PCBM) with two styryl groups. The spin-coated bis-PCBVB film was cross-linked in situ by heating at 170 °C for 60 min. Surface characterizations by UV-visible absorption, atomic force microscopy, and photoelectron yield spectroscopy revealed that a smooth and solvent-resistant film (p-PCBVB) was obtained. In bilayer films with a donor conjugated polymer, poly[2,7-(9,9-didodecylfluorene)-alt-5,5-(4',7'-bis(2-thienyl)-2',1',3'-benzothiadiazole)] (PF12TBT), spin-coated on top of the p-PCBVB acceptor layer, the photoluminescence (PL) of the PF12TBT was effectively quenched. This is because the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the p-PCBVB film are nearly the same as those of the parent bis-PCBM spin-coated film. On the basis of the PL quenching results, the exciton diffusion length and exciton diffusion coefficient in the PF12TBT were evaluated to be 11 nm and 9.8 × 10(-4) cm(2) s(-1), respectively.
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Affiliation(s)
- Yanbin Wang
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University , Katsura, Nishikyo, Kyoto 615-8510, Japan
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Chen S, Xiao Z, He D, Ma L, Ding L. Function of CH2Addends on 54π Fullerene Acceptors. ASIAN J ORG CHEM 2014. [DOI: 10.1002/ajoc.201402104] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Trukhanov VA, Paraschuk DY. Non-fullerene acceptors for organic solar cells. POLYMER SCIENCE SERIES C 2014. [DOI: 10.1134/s181123821401010x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
High-performance solution-processed organic semiconductors maintain macroscopic functionality even in the presence of microscopic disorder. Here we show that the functional robustness of certain organic materials arises from the ability of molecules to create connected mesoscopic electrical networks, even in the absence of periodic order. The hierarchical network structures of two families of important organic photovoltaic acceptors, functionalized fullerenes and perylene diimides, are analyzed using a newly developed graph methodology. The results establish a connection between network robustness and molecular topology, and also demonstrate that solubilizing moieties play a large role in disrupting the molecular networks responsible for charge transport. A clear link is established between the success of mono and bis functionalized fullerene acceptors in organic photovoltaics and their ability to construct mesoscopically connected electrical networks over length scales of 10 nm.
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Muth MA, Mitchell W, Tierney S, Lada TA, Xue X, Richter H, Carrasco-Orozco M, Thelakkat M. Influence of charge carrier mobility and morphology on solar cell parameters in devices of mono- and bis-fullerene adducts. NANOTECHNOLOGY 2013; 24:484001. [PMID: 24196215 DOI: 10.1088/0957-4484/24/48/484001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Herein, we analyze charge carrier mobility and morphology of the active blend layer in thin film organic solar cells and correlate them with device parameters. A low band gap donor-acceptor copolymer in combination with phenyl-C61-butyric acid methyl ester (PCBM) or two bis-adduct fullerenes, bis-PCBM and bis-o-quino-dimethane C60 (bis-oQDMC), is investigated. We study the charge transport of polymer:fullerene blends in hole- and electron-only devices using the space-charge limited current method. Lower electron mobilities are observed in both bis-adduct fullerene blends. Hole mobility, however, is decreased only in the blend containing bis-oQDMC. Both bis-adduct fullerene blends show very high open circuit voltage in solar cell devices, but poor photocurrent compared to the standard PCBM blend for an active layer thickness of 200 nm. Therefore, a higher short circuit current is feasible for the polymer:bis-PCBM blend by reducing the active layer thickness in order to compensate for the low electron mobility, which results in a PCE of 4.3%. For the polymer:bis-oQDMC blend, no such improvement is achieved due to an unfavorable morphology in this particular blend system. The results are supported by external quantum efficiency measurements, atomic force microscopy, transmission electron microscopy and UV/vis spectroscopy. Based on these results, the investigations presented herein give a more scientific basis for the optimization of solar cells.
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Affiliation(s)
- Mathis-Andreas Muth
- Applied Functional Polymers, Department of Macromolecular Chemistry I, University of Bayreuth, Universitätsstraße 30, D-95440 Bayreuth, Germany. Merck Chemicals Ltd, Chilworth Technical Centre, University Parkway, Southampton SO16 7QD, UK
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9
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Kang H, Kim KH, Kang TE, Cho CH, Park S, Yoon SC, Kim BJ. Effect of fullerene tris-adducts on the photovoltaic performance of P3HT:fullerene ternary blends. ACS APPLIED MATERIALS & INTERFACES 2013; 5:4401-4408. [PMID: 23574307 DOI: 10.1021/am400695e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Fullerene tris-adducts have the potential of achieving high open-circuit voltages (V(OC)) in bulk heterojunction (BHJ) polymer solar cells (PSCs), because their lowest unoccupied molecular orbital (LUMO) level is higher than those of fullerene mono- and bis-adducts. However, no successful examples of the use of fullerene tris-adducts as electron acceptors have been reported. Herein, we developed a ternary-blend approach for the use of fullerene tris-adducts to fully exploit the merit of their high LUMO level. The compound o-xylenyl C60 tris-adduct (OXCTA) was used as a ternary acceptor in the model system of poly(3-hexylthiophene) (P3HT) as the electron donor and the two soluble fullerene acceptors of OXCTA and fullerene monoadduct (o-xylenyl C60 monoadduct (OXCMA), phenyl C61-butyric acid methyl ester (PCBM), or indene-C60 monoadduct (ICMA)). To explore the effect of OXCTA in ternary-blend PSC devices, the photovoltaic behavior of the device was investigated in terms of the weight fraction of OXCTA (W(OXCTA)). When W(OXCTA) is small (<0.3), OXCTA can generate a synergistic bridging effect between P3HT and the fullerene monoadduct, leading to simultaneous enhancement in both V(OC) and short-circuit current (J(SC)). For example, the ternary PSC devices of P3HT:(OXCMA:OXCTA) with W(OXCTA) of 0.1 and 0.3 exhibited power-conversion efficiencies (PCEs) of 3.91% and 3.96%, respectively, which were significantly higher than the 3.61% provided by the P3HT:OXCMA device. Interestingly, for W(OXCTA) > 0.7, both V(OC) and PCE of the ternary-blend PSCs exhibited nonlinear compositional dependence on W(OXCTA). We noted that the nonlinear compositional trend of P3HT:(OXCMA:OXCTA) was significantly different from that of P3HT:(OXCMA:o-xylenyl C60 bis-adduct (OXCBA)) ternary-blend PSC devices. The fundamental reasons for the differences between the photovoltaic trends of the two different ternary-blend systems were investigated systemically by comparing their optical, electrical, and morphological properties.
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Affiliation(s)
- Hyunbum Kang
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea
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10
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Akaike K, Kanai K, Ouchi Y, Seki K. Side chain effect on electronic structure of spin-coated films of [6,6]-phenyl-C61-butyric acid methyl ester and its bis-adduct. Chem Phys 2013. [DOI: 10.1016/j.chemphys.2013.02.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Kang TE, Cho HH, Cho CH, Kim KH, Kang H, Lee M, Lee S, Kim B, Im C, Kim BJ. Photoinduced charge transfer in donor-acceptor (DA) copolymer: fullerene bis-adduct polymer solar cells. ACS APPLIED MATERIALS & INTERFACES 2013; 5:861-868. [PMID: 23289501 DOI: 10.1021/am302479u] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Polymer solar cells (PSCs) consisting of fullerene bis-adduct and poly(3-hexylthiophene) (P3HT) blends have shown higher efficiencies than P3HT:phenyl C(61)-butyric acid methyl ester (PCBM) devices, because of the high-lying lowest unoccupied molecular orbital (LUMO) level of the fullerene bis-adducts. In contrast, the use of fullerene bis-adducts in donor-acceptor (DA) copolymer systems typically causes a decrease in the device's performance due to the decreased short-circuit current (J(SC)) and the fill factor (FF). However, the reason for such poor performance in DA copolymer:fullerene bis-adduct blends is not fully understood. In this work, bulk-heterojunction (BHJ)-type PSCs composed of three different electron donors with four different electron acceptors were chosen and compared. The three electron donors were (1) poly[(4,8-bis-(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene)-2,6-diyl-alt-(5-octylthieno[3,4-c]pyrrole-4,6-dione)-1,3-diyl] (PBDTTPD), (2) poly[(4,8-bis-(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene)-2,6-diyl] (PBDTTT-C), and (3) P3HT polymers. The four electron acceptors were (1) PCBM, (2) indene-C(60) monoadduct (ICMA), (3) indene-C(60) bis-adduct (ICBA), and (4) indene-C(60) tris-adduct (ICTA). To understand the difference in the performance of BHJ-type PSCs for the three different polymers in terms of the choice of fullerene acceptor, the structural, optical, and electrical properties of the blends were measured by the external quantum efficiency (EQE), photoluminescence, grazing incidence X-ray scattering, and transient absorption spectroscopy. We observed that while the molecular packing and optical properties cannot be the main reasons for the dramatic decrease in the PCE of the DA copolymers and ICBA, the value of the driving force for charge transfer (ΔG(CT)) is a key parameter for determining the change in J(SC) and device efficiency in the DA copolymer- and P3HT-based PSCs in terms of fullerene acceptor. The low EQE and J(SC) in PBDTTPD and PBDTTT-C blended with ICBA and ICTA were attributed to an insufficient ΔG(CT) due to the higher LUMO levels of the fullerene multiadducts. Quantitative information on the efficiency of the charge transfer was obtained by comparing the polaron yield, lifetime, and exciton dissociation probability in the DA copolymer:fullerene acceptor films.
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Affiliation(s)
- Tae Eui Kang
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
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Sen K, Crespo-Otero R, Weingart O, Thiel W, Barbatti M. Interfacial States in Donor-Acceptor Organic Heterojunctions: Computational Insights into Thiophene-Oligomer/Fullerene Junctions. J Chem Theory Comput 2012; 9:533-42. [PMID: 26589052 DOI: 10.1021/ct300844y] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Donor-acceptor heterojunctions composed of thiophene oligomers and C60 fullerene were investigated with computational methods. Benchmark calculations were performed with time-dependent density functional theory. The effects of varying the density functional, the number of oligomers, the intermolecular distance, the medium polarization, and the chemical functionalization of the monomers were analyzed. The results are presented in terms of diagrams where the electronic states are classified as locally excited states, charge-transfer states, and delocalized states. The effects of each option for computational simulations of realistic heterojunctions employed in photovoltaic devices are evaluated and discussed.
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Affiliation(s)
- Kakali Sen
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1, D-45470 Mülheim, Germany
| | - Rachel Crespo-Otero
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1, D-45470 Mülheim, Germany
| | - Oliver Weingart
- Institut für Theoretische Chemie und Computerchemie, Heinrich-Heine-Universität Düsseldorf , Universitätsstrasse 1, D-40225 Düsseldorf, Germany
| | - Walter Thiel
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1, D-45470 Mülheim, Germany
| | - Mario Barbatti
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1, D-45470 Mülheim, Germany
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Bernardi M, Palummo M, Grossman JC. Semiconducting monolayer materials as a tunable platform for excitonic solar cells. ACS NANO 2012; 6:10082-10089. [PMID: 23062107 DOI: 10.1021/nn303815z] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The recent advent of two-dimensional monolayer materials with tunable optical properties and high carrier mobility offers renewed opportunities for efficient, ultrathin excitonic solar cells alternative to those based on conjugated polymer and small molecule donors. Using first-principles density functional theory and many-body calculations, we demonstrate that monolayers of hexagonal BN and graphene (CBN) combined with commonly used acceptors such as PCBM fullerene or semiconducting carbon nanotubes can provide excitonic solar cells with tunable absorber gap, donor-acceptor interface band alignment, and power conversion efficiency, as well as novel device architectures. For the case of CBN-PCBM devices, we predict power conversion efficiency limits in the 10-20% range depending on the CBN monolayer structure. Our results demonstrate the possibility of using monolayer materials in tunable, efficient, ultrathin solar cells in which unexplored exciton and carrier transport regimes are at play.
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Affiliation(s)
- Marco Bernardi
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge Massachusetts 02139-4307, United States
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14
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Guilbert AAY, Reynolds LX, Bruno A, MacLachlan A, King SP, Faist MA, Pires E, Macdonald JE, Stingelin N, Haque SA, Nelson J. Effect of multiple adduct fullerenes on microstructure and phase behavior of P3HT:fullerene blend films for organic solar cells. ACS NANO 2012; 6:3868-3875. [PMID: 22533706 DOI: 10.1021/nn204996w] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The bis and tris adducts of [6,6]phenyl-C(61)-butyric acid methyl ester (PCBM) offer lower reduction potentials than PCBM and are therefore expected to offer larger open-circuit voltages and more efficient energy conversion when blended with conjugated polymers in photovoltaic devices in place of PCBM. However, poor photovoltaic device performances are commonly observed when PCBM is replaced with higher-adduct fullerenes. In this work, we use transmission electron microscopy (TEM), steady-state and ultrafast time-resolved photoluminescence spectroscopy (PL), and differential scanning calorimetry (DSC) to probe the microstructural properties of blend films of poly(3-hexylthiophene-2,5-diyl) (P3HT) with the bis and tris adducts of PCBM. TEM and PL indicate that, in as-spun blend films, fullerenes become less soluble in P3HT as the number of adducts increases. PL indicates that upon annealing crystallization leads to phase separation in P3HT:PCBM samples only. DSC studies indicate that the interactions between P3HT and the fullerene become weaker with higher-adduct fullerenes and that all systems exhibit eutectic phase behavior with a eutectic composition being shifted to higher molar fullerene content for higher-adduct fullerenes. We propose two different mechanisms of microstructure development for PCBM and higher-adduct fullerenes. P3HT:PCBM blends, phase segregation is the result of crystallization of either one or both components and is facilitated by thermal treatments. In contrast, for blends containing higher adducts, the phase separation is due to a partial demixing of the amorphous phases. We rationalize the lower photocurrent generation by the higher-adduct fullerene blends in terms of film microstructure.
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Affiliation(s)
- Anne A Y Guilbert
- Centre for Plastic Electronics and Department of Physics, Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom
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15
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Cates N, Sweetnam S, Hoke ET, Gysel R, Miller CE, Bartelt JA, Xie X, Toney MF, McGehee MD. Molecular packing and solar cell performance in blends of polymers with a bisadduct fullerene. NANO LETTERS 2012; 12:1566-1570. [PMID: 22375600 DOI: 10.1021/nl204421p] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We compare the solar cell performance of several polymers with the conventional electron acceptor phenyl-C61-butyric acid methyl ester (PCBM) to fullerenes with one to three indene adducts. We find that the multiadduct fullerenes with lower electron affinity improve the efficiency of the solar cells only when they do not intercalate between the polymer side chains. When they intercalate between the side chains, the multiadduct fullerenes substantially reduce solar cell photocurrent. We use X-ray diffraction to determine how the fullerenes are arranged within crystals of poly-(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) and suggest that poor electron transport in the molecularly mixed domains may account for the reduced solar cell performance of blends with fullerene intercalation.
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Affiliation(s)
- Nichole Cates
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA
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Ye G, Chen S, Xiao Z, Zuo Q, Wei Q, Ding L. o-Quinodimethane-methano[60]fullerene and thieno-o-quinodimethane-methano[60]fullerene as efficient acceptor materials for polymer solar cells. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm35247h] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Kang H, Cho CH, Cho HH, Kang TE, Kim HJ, Kim KH, Yoon SC, Kim BJ. Controlling number of indene solubilizing groups in multiadduct fullerenes for tuning optoelectronic properties and open-circuit voltage in organic solar cells. ACS APPLIED MATERIALS & INTERFACES 2012; 4:110-116. [PMID: 22148504 DOI: 10.1021/am201075y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The ability to tune the lowest unoccupied molecular orbital (LUMO)/highest occupied molecular orbital (HOMO) levels of fullerene derivatives used as electron acceptors is crucial in controlling the optical/electrochemical properties of these materials and the open circuit voltage (V(oc)) of solar cells. Here, we report a series of indene fullerene multiadducts (ICMA, ICBA, and ICTA) in which different numbers of indene solubilizing groups are attached to the fullerene molecule. The addition of indene units to fullerene raised its LUMO and HOMO levels, resulting in higher V(oc) values in the photovoltaic device. Bulk-heterojunction (BHJ) solar cells fabricated from poly(3-hexylthiophene) (P3HT) and a series of fullerene multiadducts-ICMA, ICBA, and ICTA showed V(oc) values of 0.65, 0.83, and 0.92 V, respectively. Despite demonstrating the highest V(oc) value, the P3HT:ICTA device exhibited lower efficiency (1.56%) than the P3HT:ICBA device (5.26%) because of its lower fill factor and current. This result could be explained by the lower light absorption and electron mobility of the P3HT:ICTA device, suggesting that there is an optimal number of the solubilizing group that can be added to the fullerene molecule. The effects of the addition of solubilizing groups on the optoelectrical properties of fullerene derivatives were carefully investigated to elucidate the molecular structure-device function relationship.
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Affiliation(s)
- Hyunbum Kang
- Department of Chemical & Biomolecular Engineering, Korea Advanced Institute Science and Technology (KAIST), Daejeon 305-701, Korea
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Liu T, Cheung DL, Troisi A. Structural variability and dynamics of the P3HT/PCBM interface and its effects on the electronic structure and the charge-transfer rates in solar cells. Phys Chem Chem Phys 2011; 13:21461-70. [PMID: 22048763 DOI: 10.1039/c1cp23084k] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Using a range of realistic interface geometries obtained from a molecular dynamics simulation we study the effects of different microscopic atomic arrangements on the electronic structure and charge transfer rates of the prototypical photovoltaic interface between P3HT (poly(3-hexylthiophene)) and PCBM ([6,6]-phenyl-C(61)-butyric acid methyl ester). The electronic structures of charge-transfer (CT) states belong to two groups that can be denoted as "charge-separated" and "charge-bridging" states. For the former group of structures, which may lead to fully separated charges, the ranges and the average values of internal reorganization energy, the electronic coupling and the charge separated states energy are evaluated. A range and distribution of absolute charge separation (CS) and recombination (CR) rates are computed using the Marcus-Levich-Jortner rate equation. Due to the variety of P3HT/PCBM interface structures, a very broad range of CS (7.7 × 10(9)-1.8 × 10(12) s(-1)) and CR (2.5 × 10(5)-1.1 × 10(10) s(-1)) "instantaneous" rates are computed. However, the energetic parameters affecting the rate evolve in time due to the dynamic nature of the interface with a characteristic timescale of about 10 ns. For this reason the slowest CR instantaneous rates are not observed and the minimum CR rate observed is determined by the rate of conformational rearrangement at the interface. The combination of these observations provides a more general framework for the interpretation of experimental spectroscopic data, suggesting that the analysis based on simple first order rates may be insufficient to describe charge transfer in organic solar cell interfaces.
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Affiliation(s)
- Tao Liu
- Department of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL, UK.
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Busby E, Rochester CW, Moulé AJ, Larsen DS. Acceptor dependent polaron recombination dynamics in poly 3-hexyl thiophene: Fullerene composite films. Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2011.07.066] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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