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Zhou, Yi
Publications (10 of 10) Show all publications
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, p. 22-30Article 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
Keywords
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
Li, W., Zhou, Y., Andersson, V., Andersson, M., Thomann, Y., Veit, C., . . . Zhang, F. (2011). The Effect of additive on performance and shelf-stability of HSX-1/PCBM photovoltaic devices. Organic electronics, 12(9), 1544-1551
Open this publication in new window or tab >>The Effect of additive on performance and shelf-stability of HSX-1/PCBM photovoltaic devices
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2011 (English)In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 12, no 9, p. 1544-1551Article in journal (Refereed) Published
Abstract [en]

How 1,8-diiodooctane (DIO) enhances performance of polymer solar cells based on polymer HXS-1 and fullerene [6,6]-phenyl C(71)-butyric acid methyl ester (PC(71)BM) from 3.6% to 5.4% is scrutinized with several techniques by comparing devices or blend films spin-coated from dichlorobenzene (DCB) to those from DCB/DIO (97.5:2.5 v/v). Morphology of blend films is examined with atomic force microscopy (AFM), transmission electron microscopy (TEM) and electron tomography (3-D TEM), respectively. Charge generation and recombination is studied with photoluminescence, and charge transport with field effect transistors. The morphology with domain size in 10-20 nm and vertical elongated clusters formed in DIO system is supposed to facilitate charge transport and minimize charge carrier recombination, which are the main reasons for enhancing power conversion efficiency (PCE) from 3.6% (without DIO) to 5.4% (with DIO). Furthermore, a two year inspection shows no significant impact of DIO on the shelf-stability of the solar cells. No visible degradation in the second year indicates that the morphology of the active layers in the devices is relatively stable after initial relaxation in the first year.

Place, publisher, year, edition, pages
Elsevier Science B.V., Amsterdam., 2011
Keywords
Polymer solar cell; Additive; Morphology; Shelf-stability; Phase separation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-69770 (URN)10.1016/j.orgel.2011.05.028 (DOI)000292685700013 ()
Note

Original Publication: Weiwei Li, Yi Zhou, Viktor Andersson, Mattias Andersson, Yi Thomann, Clemens Veit, Kristofer Tvingstedt, Ruiping Qin, Zhishan Bo, Olle Inganäs, Uli Wuerfel and Fengling Zhang, The Effect of additive on performance and shelf-stability of HSX-1/PCBM photovoltaic devices, 2011, Organic electronics, (12), 9, 1544-1551. http://dx.doi.org/10.1016/j.orgel.2011.05.028 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/

Available from: 2011-08-10 Created: 2011-08-08 Last updated: 2017-12-08Bibliographically approved
Zhou, Y., Antenehe Gedefaw, D., Hellstrom, S., Kratschmer, I., Zhang, F., Mammo, W., . . . Andersson, M. R. (2010). Black Polymers in Bulk-Heterojunction Solar Cells. IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, 16(6), 1565-1572
Open this publication in new window or tab >>Black Polymers in Bulk-Heterojunction Solar Cells
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2010 (English)In: IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, ISSN 1077-260X, Vol. 16, no 6, p. 1565-1572Article in journal (Refereed) Published
Abstract [en]

The active materials in polymer solar cells have a decisive role on the performance of the cells. Polymers with extended absorption, i.e., black polymers with absorption covering the whole visible region are desired in order to capture the important parts of the solar irradiation. Different ways of achieving black active materials are discussed and two new alternating polyfluorene (APFO) copolymers with broad absorption, APFO-Black 1 and APFO-Black 2, using two different design strategies are described. The UV-Vis absorption spectra of the polymers extend to approximately 850 nm, and the polymers were used as donors and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM)[60] or PCBM[70] as acceptors in solar cell devices in various mixing ratios. The best combinations yielded an overall power conversion efficiency of 1.2% for APFO-Black 1 and 1.5% for APFO-Black 2.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2010
Keywords
Atomic force microscopy (AFM), charge-carrier mobility, fullerene, photovoltaic cell materials, solar energy
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-67161 (URN)10.1109/JSTQE.2010.2049002 (DOI)000288488400008 ()
Available from: 2011-04-01 Created: 2011-04-01 Last updated: 2015-06-01
Müller, C., Wang, E., Andersson, M., Tvingstedt, K., Zhou, Y., Andersson, M. R. & Inganäs, O. (2010). Influence of Molecular Weight on the Performance of Organic Solar Cells Based on a Fluorene Derivative. ADVANCED FUNCTIONAL MATERIALS, 20(13), 2124-2131
Open this publication in new window or tab >>Influence of Molecular Weight on the Performance of Organic Solar Cells Based on a Fluorene Derivative
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2010 (English)In: ADVANCED FUNCTIONAL MATERIALS, ISSN 1616-301X, Vol. 20, no 13, p. 2124-2131Article in journal (Refereed) Published
Abstract [en]

The performance of organic photovoltaic (OPV) bulk-heterojunction blends comprising a liquid-crystalline fluorene derivative and a small-molecular fullerene is found to increase asymptotically with the degree of polymerization of the former. Similar to various thermodynamic transition temperatures as well as the light absorbance of the fluorene moiety, the photocurrent extracted from OPV devices is found to strongly vary with increasing oligomer size up to a number average molecular weight, M-n approximate to 10 kg mol(-1), but is rendered less chain-length dependent for higher M-n as the fluorene derivative gradually adopts polymeric behavior.

Place, publisher, year, edition, pages
John Wiley and Sons, Ltd, 2010
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-58539 (URN)10.1002/adfm.201000224 (DOI)000280276900013 ()
Available from: 2010-08-13 Created: 2010-08-13 Last updated: 2015-05-29
Cai, T., Zhou, Y., Wang, E., Hellstrom, S., Zhang, F., Xu, S., . . . Andersson, M. R. (2010). Low bandgap polymers synthesized by FeCol(3) oxidative polymerization. SOLAR ENERGY MATERIALS AND SOLAR CELLS, 94(7), 1275-1281
Open this publication in new window or tab >>Low bandgap polymers synthesized by FeCol(3) oxidative polymerization
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2010 (English)In: SOLAR ENERGY MATERIALS AND SOLAR CELLS, ISSN 0927-0248, Vol. 94, no 7, p. 1275-1281Article in journal (Refereed) Published
Abstract [en]

Four low bandgap polymers, combining an alkyl thiophene donor with benzo[c][1,2,5]thiadiazole, 2,3-diphenylquinoxaline, 2,3-diphenylthieno[3,4-b]pyrazine and 6,7-diphenyl-[1,2,5]thiadiazolo[3,4-g] quinoxaline acceptors in a donor-acceptor-donor architecture, were synthesized via FeCl3 oxidative polymerization. The molecular weights of the polymers were improved by introducing o-dichlor-obenzene (ODCB) as the reaction solvent instead of the commonly used solvent, chloroform. The photophysical, electrochemical and photovoltaic properties of the resulting polymers were investigated and compared. The optical bandgaps of the polymers vary between 1.0 and 1.9 eV, which is promising for solar cells. The devices spin-coated from an ODCB solution of P1DB:[70]PCBM showed a power conversion efficiency of 1.08% with an open-circuit voltage of 0.91 V and a short-circuit current density of 3.36 mA cm(-2) under irradiation from an AM1.5G solar simulator (100 mW cm(-2)).

Place, publisher, year, edition, pages
Elsevier Science B.V., Amsterdam., 2010
Keywords
Polymer solar cells, Bulk heterojunction, FeCl3 oxidative polymerization, Low bandgap polymers, Benzo[c][1, 2, 5]thiadiazole
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-57382 (URN)10.1016/j.solmat.2010.03.024 (DOI)000278376500015 ()
Available from: 2010-06-18 Created: 2010-06-18 Last updated: 2015-05-29
He, Y., Zhou, Y., Zhao, G., Min, J., Guo, X., Zhang, B., . . . Inganäs, O. (2010). Poly(4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b ]dithiophene vinylene): Synthesis, Optical and Photovoltaic Properties. JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY, 48(8), 1822-1829
Open this publication in new window or tab >>Poly(4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b ]dithiophene vinylene): Synthesis, Optical and Photovoltaic Properties
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2010 (English)In: JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY, ISSN 0887-624X, Vol. 48, no 8, p. 1822-1829Article in journal (Refereed) Published
Abstract [en]

A new benzodithiophene (BDT)-based polymer, poly(4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b]dithiophene vinylene) (PBDTV), was synthesized by Pd-catalyzed Stille-coupling method. The polymer is soluble in common organic solvents and possesses high thermal stability. PBDTV film shows a broad absorption band covering from 350 nm to 618 nm, strong photoluminescence peaked at 545 nm and high hole mobility of 4.84 x 10(-3) cm(2)/Vs. Photovoltaic properties of PBDTV were studied by fabricating the polymer solar cells based on PBDTV as donor and PC70BM as acceptor. With the weight ratio of PBDTV: PC70BM of 1:4 and the active layer thickness of 65 nm, the power conversion efficiency of the device reached 2.63% with V-oc = 0.71 V, I-sc = 6.46 mA/cm(2), and FF = 0.57 under the illumination of AM1.5, 100 mW/cm(2).

Place, publisher, year, edition, pages
John Wiley and Sons, Ltd, 2010
Keywords
conjugated polymers, PC70BM, poly(benzodithiophene vinylene), polymer solar cells, synthesis, UV-Vis spectroscopy
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-56298 (URN)10.1002/pola.23952 (DOI)000276976300017 ()
Available from: 2010-05-07 Created: 2010-05-07 Last updated: 2015-05-29
Hellstrom, S., Lindgren, L. J., Zhou, Y., Zhang, F., Inganäs, O. & Andersson, M. R. (2010). Synthesis and characterization of three small band gap conjugated polymers for solar cell applications. POLYMER CHEMISTRY, 1(8), 1272-1280
Open this publication in new window or tab >>Synthesis and characterization of three small band gap conjugated polymers for solar cell applications
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2010 (English)In: POLYMER CHEMISTRY, ISSN 1759-9954, Vol. 1, no 8, p. 1272-1280Article in journal (Refereed) Published
Abstract [en]

We report on a new series of small band gap conjugated polymers utilizing donor-acceptor-donor substructures in the polymer backbone to broaden and extend the optical absorption to longer wavelengths. Three polymers were prepared by Suzuki polymerization, using the same donor-acceptor-donor segment but with different comonomers. The goal was to investigate how the optical and electronic properties of the polymers were influenced by the different comonomers. Electrochemical spectroscopy, using square-wave voltammetry, shows that increasing the electron-donating strength of the comonomer will raise the HOMO energy level of the polymer, resulting in a decreased band gap. This result is also manifested by comparing open-circuit voltages from the corresponding laboratory fabricated solar cells. The best performing photovoltaic cell, based on APFO-Green15/[60]PCBM (1 : 4 w/w), reached a J(sc) of 4.2 mA cm(-2), a V-oc of 0.73 V, and a FF of 0.54, giving a PCE of 1.7%.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2010
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-60691 (URN)10.1039/c0py00152j (DOI)000282612700014 ()
Available from: 2010-11-01 Created: 2010-10-22 Last updated: 2015-05-29
Li, W., Qin, R., Zhou, Y., Andersson, M., Li, F., Zhang, C., . . . Zhang, F. (2010). Tailoring side chains of low band gap polymers for high efficiency polymer solar cells. Polymer, 51(14), 3031-3038
Open this publication in new window or tab >>Tailoring side chains of low band gap polymers for high efficiency polymer solar cells
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2010 (English)In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 51, no 14, p. 3031-3038Article in journal (Refereed) Published
Abstract [en]

High efficiency organic solar cells (OSCs) require conjugated polymers with a low band gap, broad absorption in visible and IR region, high carrier mobility, and relatively high molecular weight as p-type donor materials. Flexible side chains on the rigid polymer backbone are crucial for the solubility of conjugated polymers. In this work, four polymers with the main chain structure of fluorene-thiophene-benzothiadiazole-thiophene and flexible side chains located on fluorene, thiophene, and benzothiadiazole moiety, respectively, have been synthesized by Suzuki-Miyaura-Schluter polycondensation. Photovoltaic device measurements with a device configuration of ITO/polymer:PC71BM blends/LiF/Al show that P1 carrying octyloxy chains on benzothiadiazole rings gives the best performance, with a power conversion efficiency of 3.1%.

Place, publisher, year, edition, pages
Elsevier Science B.V., Amsterdam., 2010
Keywords
Organic solar cell; Side chains; Low band gap
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-58286 (URN)10.1016/j.polymer.2010.05.015 (DOI)000279181400013 ()
Available from: 2010-08-10 Created: 2010-08-09 Last updated: 2017-12-12
Li, W., Du, C., Li, F., Zhou, Y., Fahlman, M., Bo, Z. & Zhang, F. (2009). Benzothiadiazole-Based Linear and Star Molecules: Design, Synthesis, and Their Application in Bulk Heterojunction Organic Solar Cells. CHEMISTRY OF MATERIALS, 21(21), 5327-5334
Open this publication in new window or tab >>Benzothiadiazole-Based Linear and Star Molecules: Design, Synthesis, and Their Application in Bulk Heterojunction Organic Solar Cells
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2009 (English)In: CHEMISTRY OF MATERIALS, ISSN 0897-4756, Vol. 21, no 21, p. 5327-5334Article in journal (Refereed) Published
Abstract [en]

Star molecules have many advantages, such as monodispersity, excellent solubility, and vast structures with different functional groups. A set of four-arm star molecules with benzothiadiazole as the core, oligothiophene its the arm, and triphenylamine its the end group and their linear counterparts were designed and synthesized Organic solar cells (OSCs) fabricated with these star molecules and [6,6]-phenyl C-71 butyric acid methyl ester (PC71BM) by spin-coating from solution demonstrate similar short circuit current density (J(sc)) and fill factor (FF) but larger open circuit voltage (V-oc) in comparison With solar cells fabricated with corresponding linear molecules and PC71BM A power conversion efficiency (PCE) of 18%, with J(sc) = 4.9 mA/cm(2), V-oc = 0 92 V, and FF = 0 41 was achieved with one of these star molecules

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-51779 (URN)10.1021/cm902611b (DOI)
Available from: 2009-11-18 Created: 2009-11-17 Last updated: 2015-05-18
Zhou, Y., Tvingstedt, K., Zhang, F., Du, C., Ni, W.-X., Andersson, M. R. & Inganäs, O. (2009). Observation of a Charge Transfer State in Low-Bandgap Polymer/Fullerene Blend Systems by Photoluminescence and Electroluminescence Studies. ADVANCED FUNCTIONAL MATERIALS, 19(20), 3293-3299
Open this publication in new window or tab >>Observation of a Charge Transfer State in Low-Bandgap Polymer/Fullerene Blend Systems by Photoluminescence and Electroluminescence Studies
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2009 (English)In: ADVANCED FUNCTIONAL MATERIALS, ISSN 1616-301X, Vol. 19, no 20, p. 3293-3299Article in journal (Refereed) Published
Abstract [en]

The presence of charge transfer states generated by the interaction between the fullerene acceptor PCBM and two alternating copolymers of fluorene with donor-acceptor-donor comonomers are reported; the generation leads to modifications in the polymer bandgap and electronic structure. In one of polymer/fullerene blends, the driving; force for photocurrent generation, i.e., the gap between the lowest unoccupied molecular orbitals of the donor and acceptor, is only 0.1 eV, but photocurrent is generated. It is shown that the presence of a charge transfer state is more important than the driving force. The charge transfer states are visible through new emission peaks in the photoluminescence spectra and through electroluminescence at a forward bias. The photoluminescence can be quenched under reverse bias, and can be directly correlated to the mechanism of photocurrent generation. The excited charge transfer state is easily dissociated into free charge carriers, and is an important intermediate state through which free charge carriers are generated.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-51897 (URN)10.1002/adfm.200900702 (DOI)
Available from: 2009-11-23 Created: 2009-11-23 Last updated: 2015-06-01
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