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Publications (7 of 7) Show all publications
Banerjee, D., Vallin, Ö., Samani, K. M., Majee, S., Zhang, S.-L., Liu, J. & Zhang, Z.-B. (2018). Elevated thermoelectric figure of merit of n-type amorphous silicon by efficient electrical doping process. Nano Energy, 44, 89-94
Open this publication in new window or tab >>Elevated thermoelectric figure of merit of n-type amorphous silicon by efficient electrical doping process
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2018 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 44, p. 89-94Article in journal (Refereed) Published
Abstract [en]

The currently dominant thermoelectric (TE) materials used in low to medium temperature range contain Tellurium that is rare and mild-toxic. Silicon is earth abundant and environment friendly, but it is characterized by a poor TE efficiency with a low figure of merit, ZT. In this work, we report that ZT of amorphous silicon (a-Si) thin films can be enhanced by 7 orders of magnitude, reaching similar to 0.64 +/- 0.13 at room temperature, by means of arsenic ion implantation followed by low-temperature dopant activation. The dopant introduction employed represents a highly controllable doping technique used in standard silicon technology. It is found that the significant enhancement of ZT achieved is primarily due to a significant improvement of electrical conductivity by doping without crystallization so as to maintain the thermal conductivity and Seebeck coefficient at the level determined by the amorphous state of the silicon films. Our results open up a new route towards enabling a-Si as a prominent TE material for cost-efficient and environment-friendly TE applications at room temperature.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keywords
Thermoelectrics, Amorphous silicon, Electrical conductivity, Electrical doping, Energy harvesting
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-341565 (URN)10.1016/j.nanoen.2017.11.060 (DOI)000419833900011 ()
Funder
Swedish Research Council, 621-2014-5596Swedish Foundation for Strategic Research , SE13-0061
Available from: 2018-02-12 Created: 2018-02-12 Last updated: 2018-02-27Bibliographically approved
Majee, S., Banerjee, D., Liu, X., Zhang, S.-L. & Zhang, Z.-B. (2017). Efficient and thermally stable iodine doping of printed graphene nano-platelets. Carbon, 117, 240-245
Open this publication in new window or tab >>Efficient and thermally stable iodine doping of printed graphene nano-platelets
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2017 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 117, p. 240-245Article in journal (Refereed) Published
Abstract [en]

We report on an efficient and highly thermally stable doping with iodine on ink-jet printed graphene films. The films consist of pristine few-layer graphene nano-platelates (p-GNPs) that are randomly stacked. With iodine doping simply by soaking in aqueous iodine solution, the printed p-GNPs films are enhanced in electrical conductivity by up to around 2 times. The doping effect exhibits excellent thermal stability up to 500 degrees C under high vacuum condition (10(-6) mBar) evidenced by electrical and spectroscopic means. Furthermore, the doping of iodine leads to a slight increment of work function by 0.07 eV. Using depth profile measurements, it is found that iodine species diffuse deeply into the films and likely intercalate between two adjacent p-GNPs which interpret the aforementioned efficient enhancement and thermal stability of the doping effect. The reported doping scheme offers a viable low-temperature optimization method for conductive electrodes with p-GNPs in the application of printed devices.

National Category
Materials Chemistry Other Physics Topics Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-322507 (URN)10.1016/j.carbon.2017.02.094 (DOI)000400212100027 ()
Funder
Swedish Foundation for Strategic Research , Dnr SE13-0061Swedish Research Council, 621-2014-5596
Available from: 2017-05-30 Created: 2017-05-30 Last updated: 2017-05-30Bibliographically approved
Majee, S. & Zhang, Z. (2016). Doping effect on the opto-electrical properties of printed graphene transparent conductive films. In: : . Paper presented at Graphene Week 2016.
Open this publication in new window or tab >>Doping effect on the opto-electrical properties of printed graphene transparent conductive films
2016 (English)Conference paper, Poster (with or without abstract) (Refereed)
Keywords
Graphene, Doping, Inkjet printing
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-281237 (URN)
Conference
Graphene Week 2016
Available from: 2016-03-21 Created: 2016-03-21 Last updated: 2016-03-23
Miao, F., Majee, S., Song, M., Zhao, J., Zhang, S. & Zhang, Z.-B. (2016). Inkjet printing of electrochemically-exfoliated graphene nano-platelets. Synthetic metals, 220, 318-322
Open this publication in new window or tab >>Inkjet printing of electrochemically-exfoliated graphene nano-platelets
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2016 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 220, p. 318-322Article in journal (Refereed) Published
Abstract [en]

In this study, we report on a facile method of inkjet printing of graphene nano-platelets (GNPs). The GNPs are exfoliated from graphite by means of an electrochemical process in an inorganic salt based electrolyte. The electrochemically exfoliated GNPs with oxygen-bearing functional groups exhibit spectroscopic features similar to those of reduced graphene oxides. As a result, ink formulation with such GNPs for inkjet printing readily accomplishes without using stabilizer and various conductive objects are easily fabricated on different substrates by inkjet printing. The as-printed films of the electrochemically exfoliated GNPs deliver an electrical conductivity of 44 S/m, a typical value for as-printed pristine GNP films in the literature. A simple thermal treatment results in an improved DC conductivity by two orders of magnitude to ~2.5 × 103 S/m.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Graphene; Electrochemical process; Inkjet printing
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-298103 (URN)10.1016/j.synthmet.2016.06.029 (DOI)000383811300040 ()
Funder
Swedish Foundation for Strategic Research , Dnr SE13-0061Swedish Research Council, 621-2014-5596
Available from: 2016-06-29 Created: 2016-06-29 Last updated: 2019-02-25Bibliographically approved
Majee, S., Song, M., Zhang, S.-L. & Zhang, Z.-B. (2016). Scalable inkjet printing of shear-exfoliated graphene transparent conductive films. Carbon, 102, 51-57
Open this publication in new window or tab >>Scalable inkjet printing of shear-exfoliated graphene transparent conductive films
2016 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 102, p. 51-57Article in journal (Refereed) Published
Abstract [en]

In this study, we demonstrate scalable and efficient inkjet printing of graphene flexible transparent conducting films (TCFs). The highly concentrated and stable graphene ink (3.2 mg/mL) that is dominated by 4-layer graphene flakes is achieved by means of shear exfoliation process. The printed graphene TCFs with DC conductivity of ∼4 × 104 S/m (sheet resistance 260 Ω/□ coupled with optical transparency of 86%) without intentional doping are readily obtained. Excellent flexibility and air stability of the printed graphene TCFs allow their potential applications in different flexible opto-electronics devices. Systematic investigation of the inkjet printing of graphene and the annealing effect on the graphene TCFs is presented.

Keywords
Graphene, Inkjet printing, Transparent conductive films
National Category
Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-276479 (URN)10.1016/j.carbon.2016.02.013 (DOI)000372808200006 ()
Funder
Swedish Foundation for Strategic Research , Dnr SE13-0061Swedish Research Council, 621-2014-5596
Available from: 2016-02-14 Created: 2016-02-14 Last updated: 2019-02-25Bibliographically approved
Majee, S., Song, M. & Zhang, Z. (2015). Printable graphene ink produced by liquid-phaseshear exfoliation of graphite. In: : . Paper presented at Advanced Materials World Congress 2015.
Open this publication in new window or tab >>Printable graphene ink produced by liquid-phaseshear exfoliation of graphite
2015 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Electrical interconnections are one of the main challenges in the printed electronics, to connect different functional units of anelectronic device. With the progressive advancement of large area and low cost printed electronic devices, the requirement forreliable interconnections with lower power consumption fabricated at low temperature is necessary. The conventional copperbased interconnections suffer severe problems in terms of cost efficiency when they are processed with photolithographytechnique. Therefore, there is being a copious amount of re-search to find alternative interconnect materials to overcome suchproblems. Recently, carbon nanotubes (Kordás et al. 2006), silver nanowires (Liu et al. 2011) and graphene (Huang et al. 2011)are being developed as the alter-native interconnection materials. Among them, graphene has high potential for suchapplication due to its remarkable inherent properties: high electrical conductivity, high transparency, mechanical flexibility,higher tensile strength, higher thermal conductivity, extremely high surface area and higher electron mobility. In spite of thoseexcellent properties, graphene has some shortcomings which are needed to be solved. Stacking of graphene sheets issues largeinterface resistance, which is responsible for poor electrical performance. Printing of graphene proved to be a promisingapproach since it combines the attractive features of graphene and the cost effective printing methods (ink-jet printing, nozzleprinting, spray printing) which enable additive patterning, direct writing, scalability to large area manufacturing. In order tofacilitate the printing process, the graphene solution needs to be highly stable, uniform and should contain smaller sheet sizes (~1μm). In this work we have proposed a cost-effective approach for large-scale production of printable stable graphene solutionto be used for the printing of inter-connects. The liquid-phase shear exfoliation (Paton, et al. 2014) of graphite allowed us toprepare large-scale production of solution with exfoliated graphene sheets. The process is scalable and requires shorterprocessing time compared to the other existing exfoliation methods. We have exfoliated graphene sheets from graphite flakesusing environmental-friendly solvent, ethanol, and a stabilizing polymer, ethyl cellulose (EC). The ethyl cellulose was used inorder to encapsulate graphene sheets in the solution and to avoid any reversible process (Secor, et al. 2013). The graphenebased solution prepared after several optimizations of the shear-mixing process leads to a stable solution for more than threemonths without any sedimentation. The microscopic studies of the films prepared from the spin-coating of the solution showedgraphene sheets without any agglomeration and with sheet sizes < 1μm. The process allowed us to prepare a cost-effectivegraphene solution which can be used for producing electrical interconnections by various printing methods.

Keywords
Graphene exfoliation; shear-mixing; interconnections; graphene ink.
National Category
Other Materials Engineering
Research subject
Materials Science
Identifiers
urn:nbn:se:uu:diva-262244 (URN)10.5185/amwc.2015 (DOI)978-91-88252-00-5 (ISBN)
Conference
Advanced Materials World Congress 2015
Available from: 2015-09-10 Created: 2015-09-10 Last updated: 2015-09-11
Majee, S., Song, M., Zhang, S. L. & Zhang, Z. (2015). Production of transparent and conductive stable graphene ink for inkjet printing method. In: : . Paper presented at EMRS Fall Meeting 2015.
Open this publication in new window or tab >>Production of transparent and conductive stable graphene ink for inkjet printing method
2015 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Electrical interconnections are one of the main challenges in the printed electronics, to connect different functional units of an electronic device. With the progressive advancement of large area and low cost printed electronic devices on polymeric and paper substrates, the requirement for reliable interconnections with lower power consumption fabricated at low temperature is necessary. The conventional copper-based interconnections suffer severe problems in terms of cost efficiency when they are processed with photolithography technique. To replace the conventional metallic interconnections we have proposed printed interconnects with graphene inks. This is mainly motivated by two reasons. First, printing is a low-cost patterning approach which is performed at ordinary ambient condition. Printing of graphene proved to be a promising since it combines the attractive features of graphene and the cost effective printing methods (ink-jet printing, nozzle printing, spray printing) which enable additive patterning, direct writing, scalability to large area manufacturing. In order to facilitate the inkjet printing process, the graphene solution needs to be highly stable, uniform and should contain smaller sheet sizes (~ 1 micro meter) because of the limitation of the nozzle size of inkjet printing machine. In this work we have proposed a cost-effective approach for large-scale production of printable stable graphene suspension by liquid-phase shear exfoliation of graphite for printed electronics application. The process is scalable and requires shorter processing time compared to the other existing exfoliation methods. Graphene sheets have been exfoliated from graphite flakes in a solvent, cyclohexanone with ethyl cellulose as stabilizer. The graphene based solution prepared after several optimizations leads to a stable ink for more than six months without any sedimentation. The initial studies confirmed the production of graphene films with average sheet thickness of 10 to 20 nm and without any agglomeration with sheet sizes less than 1 micro meter. The rheological properties, such as, viscosity, of the produced graphene ink has been carefully tuned in order for successful inkjet printing process. Highly conductive and transparent (~70 % in the visible region) interconnections have been developed after several inkjet printing steps.

National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-260202 (URN)
Conference
EMRS Fall Meeting 2015
Available from: 2015-08-17 Created: 2015-08-17 Last updated: 2016-04-22
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7825-9501

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