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Zhang, Fengling
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Publications (10 of 132) Show all publications
Gedefaw, D., Zaifei, Z., Mulugeta, E., Zhao, Y., Zhang, F., Andersson, M. R. & Mammo, W. (2016). An alternating copolymer of fluorene donor and quinoxaline acceptor versus a terpolymer consisting of fluorene, quinoxaline and benzothiadiazole building units: synthesis and characterization. Polymer Bulletin, 73(4), 1167-1183.
Open this publication in new window or tab >>An alternating copolymer of fluorene donor and quinoxaline acceptor versus a terpolymer consisting of fluorene, quinoxaline and benzothiadiazole building units: synthesis and characterization
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2016 (English)In: Polymer Bulletin, ISSN 0170-0839, E-ISSN 1436-2449, Vol. 73, no 4, 1167-1183 p.Article in journal (Refereed) Published
Abstract [en]

An alternating polyfluorene copolymer based on fluorene donor and quinoxaline acceptor (P1) and an alternating terpolymer (P2) with fluorene (50 %) donor and quinoxaline (25 %) and benzothiadiazole (25 %) acceptor units were designed and synthesized for use as photoactive materials in solar cells. The presence of benzothiadiazole unit in P2 increased the optical absorption coverage in the range of 350-600 nm, which is an interesting property and a big potential for achieving improved photovoltaic performances with judicious optimization of the devices. Solar cells were fabricated from 1:4 blends of polymers-PCBM[70] using o-dichlorobenzene (o-DCB) as processing solvent, and P1 showed a power conversion efficiency (PCE) of 3.18 %, with a short-circuit current density (J (SC)) of 7.78 mA/cm(2), an open-circuit voltage (V (OC)) of 0.82 V, and a fill factor (FF) of 50 % while P2 showed an overall PCE of 2.14 % with corresponding J (SC) of 5.97 mA/cm(2), V (OC) of 0.84 V and FF of 42 %. In general, P2 gave lower J (SC) and FF presumably due to the fine domain sizes of the polymer-PCBM[70] blend as seen from the atomic force microscopy (AFM) image which might have affected the charge carrier transport. Alternating (P1) and ternary (P2) conjugated polymers were designed, synthesized and used for fabrication of photovoltaic devices. [GRAPHICS] .

Place, publisher, year, edition, pages
SPRINGER, 2016
Keyword
Polyfluorenes; Suzuki coupling reaction; Fluorene; Quinoxaline; Benzothiadiazole
National Category
Biological Sciences
Identifiers
urn:nbn:se:liu:diva-127259 (URN)10.1007/s00289-015-1541-y (DOI)000372614700016 ()
Note

Funding Agencies|International Science Programme (ISP), Uppsala University, Sweden

Available from: 2016-04-20 Created: 2016-04-19 Last updated: 2017-11-30
Zhang, F., Inganäs, O., Zhou, Y. & Vandewal, K. (2016). Development of polymer-fullerene solar cells. NATIONAL SCIENCE REVIEW, 3(2), 222-239.
Open this publication in new window or tab >>Development of polymer-fullerene solar cells
2016 (English)In: NATIONAL SCIENCE REVIEW, ISSN 2095-5138, Vol. 3, no 2, 222-239 p.Article, review/survey (Refereed) Published
Abstract [en]

Global efforts and synergetic interdisciplinary collaborations on solution-processed bulk-heterojunction polymer solar cells (PSCs or OPVs) made power conversion efficiencies over 10% possible. The rapid progress of the field is credited to the synthesis of a large number of novel polymers with specially tunable optoelectronic properties, a better control over the nano-morphology of photoactive blend layers, the introduction of various effective interfacial layers, new device architectures and a deeper understanding of device physics. We will review the pioneering materials for polymer-fullerene solar cells and trace the progress of concepts driving their development. We discuss the evolution of morphology control, interfacial layers and device structures fully exploring the potential of photoactive materials. In order to guide a further increase in power conversion efficiency of OPV, the current understanding of the process of free charge carrier generation and the origin of the photovoltage is summarized followed by a perspective on how to overcome the limitations for industrializing PSCs.

Place, publisher, year, edition, pages
OXFORD UNIV PRESS, 2016
Keyword
polymer-fullerene solar cells; electron donors and acceptors; morphology; interfacial layer; device physics
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:liu:diva-130434 (URN)10.1093/nsr/nww020 (DOI)000379759700024 ()
Note

Funding Agencies|Swedish Research Council (VR); Swedish Energy Agency (EM) [VR 621-2013-5561, EM 42033-1]; Knut and Alice Wallenberg Foundation; National Natural Science Foundation of China [21474035]; InnoProfile project organische pin Bauelemente 2.2 [03IPT602X]

Available from: 2016-08-07 Created: 2016-08-05 Last updated: 2016-08-07
Tang, Z., Liu, B., Melianas, A., Bergqvist, J., Tress, W., Bao, Q., . . . Zhang, F. (2015). A New Fullerene-Free Bulk-Heterojunction System for Efficient High-Voltage and High-Fill Factor Solution-Processed Organic Photovoltaics. Advanced Materials, 27(11), 1900-+.
Open this publication in new window or tab >>A New Fullerene-Free Bulk-Heterojunction System for Efficient High-Voltage and High-Fill Factor Solution-Processed Organic Photovoltaics
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2015 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 27, no 11, 1900-+ p.Article in journal (Refereed) Published
Abstract [en]

Small molecule donor/polymer acceptor bulk-heterojunction films with both compounds strongly absorbing have great potential for further enhancement of the performance of organic solar cells. By employing a newly synthesized small molecule donor with a commercially available polymer acceptor in a solution-processed fullerene-free system, a high power conversion efficiency of close to 4% is reported.

Place, publisher, year, edition, pages
Wiley-VCH Verlag, 2015
National Category
Biological Sciences Physical Sciences
Identifiers
urn:nbn:se:liu:diva-116947 (URN)10.1002/adma.201405485 (DOI)000351216500012 ()25645709 (PubMedID)
Note

Funding Agencies|Swedish Energy Agency; Knut and Alice Wallenberg foundation; Swedish research council (VR); Chinese scholarship council

Available from: 2015-04-10 Created: 2015-04-10 Last updated: 2017-12-04
Bai, S., He, S., Jin, Y., Wu, Z., Xia, Z., Sun, B., . . . Zhang, F. (2015). Electrophoretic deposited oxide thin films as charge transporting interlayers for solution-processed optoelectronic devices: the case of ZnO nanocrystals. RSC Advances, 5(11), 8216-8222.
Open this publication in new window or tab >>Electrophoretic deposited oxide thin films as charge transporting interlayers for solution-processed optoelectronic devices: the case of ZnO nanocrystals
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2015 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 11, 8216-8222 p.Article in journal (Refereed) Published
Abstract [en]

A promising fabrication method of electron transporting interlayers for solution-processed optoelectronic devices by electrophoretic deposition (EPD) of colloidal zinc oxide (ZnO) nanocrystals was demonstrated. A low voltage of 3-5 V and a short deposition time of 40 s at room temperature were found to be sufficient to generate dense and uniform ZnO thin films. The EPD ZnO nanocrystal films were applied as ETLs for inverted organic solar cell and polymer light emitting diodes (PLEDs). By optimizing the EPD processing of ZnO nanocrystal electron transporting layers (ETLs), inverted organic solar cells based on [3,4-b]-thiophene/benzodithiophene (PTB7): [6-6]-phenyl-C71-butyric acid methyl ester (PC71BM) and poly(3-hexylthiophene) (P3HT): [6-6]-phenyl-C-61-butyric acid methyl ester (PC61BM) with an average PCE of 8.4% and 4.0% were fabricated. In combination with the PLEDs and flexible devices results, we conclude that the EPD processed ZnOnanocrystal thin films can serve as high quality ETLs for solution-processed optoelectronic devices.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2015
National Category
Biological Sciences
Identifiers
urn:nbn:se:liu:diva-115011 (URN)10.1039/c4ra09765c (DOI)000347720900057 ()
Note

Funding Agencies|National High Technology Research and Development Program of China [2011AA050520]; National Basic Research Program of China (973 Program) [2012CB932402]; National Natural Science Foundation of China [51172203]; Natural Science Funds for Distinguished Young Scholar of Zhejiang Province [R4110189]; Public Welfare Project of Zhejiang Province [2013C31057]; Swedish Energy Agency (Energimyndigheten); Swedish Research Council (VR)

Available from: 2015-03-09 Created: 2015-03-06 Last updated: 2017-12-04
Bai, S., Jin, Y., Liang, X., Ye, Z., Wu, Z., Sun, B., . . . Zhang, F. (2015). Ethanedithiol Treatment of Solution-Processed ZnO Thin Films: Controlling the Intragap States of Electron Transporting Interlayers for Efficient and Stable Inverted Organic Photovoltaics. ADVANCED ENERGY MATERIALS, 5(5), 1401606.
Open this publication in new window or tab >>Ethanedithiol Treatment of Solution-Processed ZnO Thin Films: Controlling the Intragap States of Electron Transporting Interlayers for Efficient and Stable Inverted Organic Photovoltaics
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2015 (English)In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 5, no 5, 1401606- p.Article in journal (Refereed) Published
Abstract [en]

The surface defects of solution-processed ZnO films lead to various intragap states. When the solution-processed ZnO films are used as electron transport interlayers (ETLs) in inverted organic solar cells, the intragap states act as interfacial recombination centers for photogenerated charges and thereby degrade the device performance. Here, a simple passivation method based on ethanedithiol (EDT) treatment is demonstrated, which effectively removes the surface defects of the ZnO nanocrystal films by forming zinc ethanedithiolates. The passivation by EDT treatment modulates the intragap states of the ZnO films and introduces a new intragap band. When the EDT-treated ZnO nanocrystal films are used as ETLs in inverted organic solar cells, both the power conversion efficiency and stability of the devices are improved. The control studies show that the solar cells with EDT-treated ZnO films exhibit reduced charge recombination rates and enhanced charge extraction properties. These features are consistent with the fact that the modulation of the intragap states results in reduction of interfacial recombination as well as the improved charge selectivity and electron transport properties of the ETLs. It is further demonstrated that the EDT treatment-based passivation method can be extended to ZnO films deposited from sol-gel precursors.

Place, publisher, year, edition, pages
Wiley-VCH Verlag, 2015
Keyword
electron transporting interlayers; intragap states; molecular passivation; organic solar cells; ZnO thin films
National Category
Biological Sciences
Identifiers
urn:nbn:se:liu:diva-116817 (URN)10.1002/aenm.201401606 (DOI)000350754800013 ()
Note

Funding Agencies|National High Technology Research and Development Program of China [2011AA050520]; National Basic Research Program of China (973 Program) [2012CB932402]; National Natural Science Foundation of China [51172203]; Natural Science Funds for Distinguished Young Scholar of Zhejiang Province [R4110189]; Public Welfare Project of Zhejiang Province [2013C31057]; Swedish Energy Agency (Energimyndigheten); Swedish Research Council (VR); European Commission under a Marie Curie Intra-European Fellowship for Career Development

Available from: 2015-04-07 Created: 2015-04-07 Last updated: 2015-06-03
Xu, B., Tian, H., Lin, L., Qian, D., Chen, H., Zhang, J., . . . Sun, L. (2015). Integrated Design of Organic Hole Transport Materials for Efficient Solid-State Dye-Sensitized Solar Cells. ADVANCED ENERGY MATERIALS, 5(3), Article ID 1401185.
Open this publication in new window or tab >>Integrated Design of Organic Hole Transport Materials for Efficient Solid-State Dye-Sensitized Solar Cells
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2015 (English)In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 5, no 3, 1401185Article in journal (Refereed) Published
Abstract [en]

A series of triphenylamine-based small molecule organic hole transport materials (HTMs) with low crystallinity and high hole mobility are systematically investigated in solid-state dye-sensitized solar cells (ssDSCs). By using the organic dye LEG4 as a photosensitizer, devices with X3 and X35 as the HTMs exhibit desirable power conversion efficiencies (PCEs) of 5.8% and 5.5%, respectively. These values are slightly higher than the PCE of 5.4% obtained by using the state-of-the-art HTM Spiro-OMeTAD. Meanwhile, transient photovoltage decay measurement is used to gain insight into the complex influences of the HTMs on the performance of devices. The results demonstrate that smaller HTMs induce faster electron recombination in the devices and suggest that the size of a HTM plays a crucial role in device performance, which is reported for the first time.

Place, publisher, year, edition, pages
Wiley-VCH Verlag, 2015
National Category
Energy Engineering
Identifiers
urn:nbn:se:liu:diva-116837 (URN)10.1002/aenm.201401185 (DOI)000350565400010 ()
Note

Funding Agencies|Swedish Research Council; Swedish Energy Agency; Knut and Alice Wallenberg Foundation; National Natural Science Foundation of China [21120102036, 91233201, 21403133]; National Basic Research Program of China (973 program) [2014CB239402]; China Scholarship Council (CSC)

Available from: 2015-04-07 Created: 2015-04-07 Last updated: 2015-04-16
Qian, D., Liu, B., Wang, S., Himmelberger, S., Linares, M., Vagin, M., . . . Zhang, F. (2015). Modulating molecular aggregation by facile heteroatom substitution of diketopyrrolopyrrole based small molecules for efficient organic solar cells. Journal of Materials Chemistry A, 3(48), 24349-24357.
Open this publication in new window or tab >>Modulating molecular aggregation by facile heteroatom substitution of diketopyrrolopyrrole based small molecules for efficient organic solar cells
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2015 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 48, 24349-24357 p.Article in journal (Refereed) Published
Abstract [en]

In conjugated polymers and small molecules of organic solar cells, aggregation induced by intermolecular interactions governs the performance of photovoltaics. However, little attention has been paid to the connection between molecular structure and aggregation within solar cells based on soluble small molecules. Here we demonstrate modulation of intermolecular aggregation of two synthesized molecules through heteroatom substitution to develop an understanding of the role of aggregation in conjugated molecules. Molecule 1 (M1) based on 2-ethylhexyloxy-benzene substituted benzo[1,2-b:4,5-b]dithiophene (BDTP) and diketopyrrolopyrrole (DPP) displays strong aggregation in commonly used organic solvents, which is reduced in molecule 2 (M2) by facile oxygen atom substitution on the BDTP unit confirmed by absorption spectroscopy and optical microscopy, while it successfully maintains molecular planarity and favorable charge transport characteristics. Solar cells based on M2 exhibit more than double the photocurrent of devices based on M1 and yield a power conversion efficiency of 5.5%. A systematic investigation of molecular conformation, optoelectronic properties, molecular packing and crystallinity as well as film morphology reveals structure dependent aggregation responsible for the performance difference between the two conjugated molecules.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2015
National Category
Biological Sciences Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-123846 (URN)10.1039/c5ta06501a (DOI)000366163000022 ()
Note

Funding Agencies|Swedish Energy Agency; China Scholarship Council (CSC)

Available from: 2016-01-11 Created: 2016-01-11 Last updated: 2017-12-01
Ma, Z., Dang, D., Tang, Z., Gedefaw, D., Bergqvist, J., Zhu, W., . . . Wang, E. (2014). A Facile Method to Enhance Photovoltaic Performance of Benzodithiophene-Isoindigo Polymers by Inserting Bithiophene Spacer. ADVANCED ENERGY MATERIALS, 4(6).
Open this publication in new window or tab >>A Facile Method to Enhance Photovoltaic Performance of Benzodithiophene-Isoindigo Polymers by Inserting Bithiophene Spacer
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2014 (English)In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 4, no 6Article in journal (Refereed) Published
Abstract [en]

A series of conjugated polymers containing benzodithiophene as donor and isoindigo as acceptor with no, one, two and three thiophene spacer groups is synthesized and characterized. The polymer with bithiophene as a spacer has a superior efficiency of 7.31% in solar cells. This demonstrates an important design strategy to produce polymers for high-performance solar cells by inserting thiophene spacer groups.

Place, publisher, year, edition, pages
Wiley-VCH Verlag, 2014
Keyword
conjugated polymers; energy conversion; fullerenes; photochemistry; solar cells
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-106976 (URN)10.1002/aenm.201301455 (DOI)000334790000008 ()
Available from: 2014-06-04 Created: 2014-06-02 Last updated: 2014-06-04
Dyer, A. L., Bulloch, R. H., Zhou, Y., Kippelen, B., Reynolds, J. R. & Zhang, F. (2014). A Vertically Integrated Solar-Powered Electrochromic Window for Energy Efficient Buildings. Advanced Materials, 26(28), 4895-4900.
Open this publication in new window or tab >>A Vertically Integrated Solar-Powered Electrochromic Window for Energy Efficient Buildings
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2014 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 28, 4895-4900 p.Article in journal (Refereed) Published
Abstract [en]

A solution-processed self-powered polymer electrochromic/photovoltaic (EC/PV) device is realized by vertically integrating two transparent PV cells with an ECD. The EC/PV cell is a net energy positive dual functional device, which can be reversibly switched between transparent and colored states by PV cells for regulating incoming sunlight through windows. The two PV cells can individually, or in pairs, generate electricity.

Place, publisher, year, edition, pages
Wiley-VCH Verlag, 2014
National Category
Biological Sciences
Identifiers
urn:nbn:se:liu:diva-109590 (URN)10.1002/adma.201401400 (DOI)000339661600020 ()24863393 (PubMedID)
Available from: 2014-08-21 Created: 2014-08-21 Last updated: 2017-12-05
Gedefaw, D. A., Zhou, Y., Ma, Z., Genene, Z., Hellstrom, S., Zhang, F., . . . Andersson, M. R. (2014). Conjugated polymers with polar side chains in bulk heterojunction solar cell devices. Polymer international, 63(1), 22-30.
Open this publication in new window or tab >>Conjugated polymers with polar side chains in bulk heterojunction solar cell devices
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2014 (English)In: Polymer international, ISSN 0959-8103, E-ISSN 1097-0126, Vol. 63, no 1, 22-30 p.Article in journal (Refereed) Published
Abstract [en]

Two polymers with polar side chains, namely poly[2,7-(9,9-dioctylfluorene)-alt-5,5-(5,8-di-2-thienyl-(2,3-bis(3-(2-(2-methoxyethoxy)ethoxy)phenyl)quinoxaline))] (P1) and poly[2,7-(9,9-bis(2-(2-methoxyethoxy)ethyl)fluorene)-alt-5,5-(5,8-di-2-thienyl-(2,3-bis(3-(2-(2-methoxyethoxy)-ethoxy)phenyl)quinoxaline))] (P2), were synthesized for solar cell application. A series of bulk heterojunction solar cells were systematically fabricated and characterized by varying the electron-acceptor materials, processing solvents and thickness of the active layer. The results show that P1, with a higher molecular weight and good film-forming properties, performed better. The best device showed an open circuit voltage of 0.87 V, a short circuit current of 6.81 mA cm(-2) and a power conversion efficiency of 2.74% with 1:4 polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM[70]) mixture using o-dichlorobenzene (o-DCB) as processing solvent. P2 on the other hand showed a poorer performance with chlorobenzene as processing solvent, but a much improved performance was obtained using o-DCB instead. Thus, an open circuit voltage of 0.80 V, short circuit current of 6.21 mA cm(-2) and an overall power conversion efficiency of 2.22% were recorded for a polymer:PCBM[70] mixing ratio of 1:4. This is presumably due to the improvement of the morphology of the active layer using o-DCB as processing solvent.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2014
Keyword
conjugated polymer, polar polymer, power conversion efficiency, donor-acceptor-donor
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-102845 (URN)10.1002/pi.4600 (DOI)000327997800004 ()
Note

Funding Agencies|International Science Programmes, Uppsala University, Sweden||

Available from: 2014-01-07 Created: 2014-01-02 Last updated: 2017-12-06
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