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Abdollahi Sani, Negar
Alternative names
Publications (4 of 4) Show all publications
Sani, N. (2016). Addressability and GHz Operation in Flexible Electronics. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Addressability and GHz Operation in Flexible Electronics
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The discovery of conductive polymers in 1977 opened up a whole new path for flexible electronics. Conducting polymers and organic semiconductors are carbon rich compounds that are able to conduct charges while flexed and are compatible with low-cost and large-scale processes including printing and coating techniques. The conducting polymer has aided the rapidly expanding field of flexible electronics, leading to many new applications such as electronic skin, RFID tags, smart labels, flexible displays, implantable medical devices, and flexible sensors.

However, there are several remaining challenges in the production and implementation of flexible electronic materials and devices. The  conductivity of organic conductors and semiconductors is still orders of magnitude lower compared to their inorganic counterparts. In addition, non-flexible inorganic semiconductors still remain the materials of choice for high frequency applications; since the charge carrier mobility and thus operational speed of the organic materials are limited. Therefore, there remains a high demand to combine the high frequency operation of inorganic semiconductors with the flexible fabrication methods of organic systems for future electronics.

In addition to the challenges in the choice of materials in flexible electronics, the upscaling of the flexible devices and implementing them in circuits can also be complicated. Lack of non-linearity is an issue that arises when flexible devices with linear behavior need to be incorporated in an array or matrix form. Non-linearity is important for applications such as displays and memory arrays, where the devices are arranged as matrix cells addressed by their row and column number. If the behavior of cells in the matrix is linear, addressing each cell affects the adjacent cells. Therefore, inducing non-linearity and, consequently, addressability in such linear devices is the first step before scaling up into matrix schemes.

In this work, non-linear organic/inorganic hybrid devices are produced to overcome the limitations mentioned above and leverage the advantages of both organic and inorganic materials. Two novel methods are developed to incorporate non-flexible inorganic semiconductors into ultra-high frequency (UHF) flexible devices. In the first method, Si is ground into a powder with micrometer-sized particles and printed through standard screen printing. For the first time, allprinted flexible diodes operating in the GHz range are produced. The energy harvesting application of the printed diodes is demonstrated in a flexible circuit coupling an antenna and the display to the diode.

A second and simpler room-temperature method based on lamination was later developed, which further improves device performance and operational frequency. For the first time, a flexible semiconducting composite film consisting of Si micro-particles, glycerol, and nano-fibrillated cellulose is produced and used as the semiconducting layer of the UHF diode.

The diodes fabricated through both mentioned processes are demonstrated in energy harvesting applications in the GHz range; however, they can also serve as rectifiers or non-linear elements in any other flexible and UHF circuit.

Furthermore, a new approach is developed to induce non-linearity and hence addressability in linear devices in order to make their implementation in flexible matrix form feasible. This is accomplished by depositing a ferroelectric layer on a device electrode and thus controlling charge transfer through the electrode. The electrode current becomes limited to the charge displacement current established in the ferroelectric layer during polarization. Thus, the current does not follow the voltage linearly and non-linearity is induced in the device. The polarization voltage is dictated by the thickness of the ferroelectric layer. Therefore, the switching voltage of the device can be tuned by adjusting the ferroelectric layer thickness. In this work, the organic ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) is used due to its distinctive properties such as stability, high polarizability and simple processability. The polarization of P(VDF-TrFE) through an electrolyte and an electrophoretic liquid is investigated. In addition, a simple model is presented in order to understand the field and potential distribution, and the ferroelectric polarization, in the P(VDF-TrFE)-electrolyte contact. The induction of non-linearity through P(VDF-TrFE) is successfully demonstrated in novel addressable and bistable devices and memory elements such as non-linear electrophoretic display cells, organic ferroelectrochromic displays (FeOECDs), and ferroelectrochemical organic transistors (FeOECTs).

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. p. 58
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1761
National Category
Physical Sciences Condensed Matter Physics Textile, Rubber and Polymeric Materials Materials Chemistry Other Electrical Engineering, Electronic Engineering, Information Engineering Polymer Chemistry
urn:nbn:se:liu:diva-127014 (URN)10.3384/diss.diva-127014 (DOI)978-91-7685-777-9 (ISBN)
Public defence
2016-05-13, K3, Kåkenhus, Campus Norrköping, Norrköping, 10:15 (English)
Available from: 2016-04-12 Created: 2016-04-12 Last updated: 2019-10-29Bibliographically approved
Abdollahi Sani, N., Wang, X., Granberg, H., Andersson Ersman, P., Crispin, X., Dyreklev, P., . . . Berggren, M. (2016). Flexible Lamination-Fabricated Ultra-High Frequency Diodes Based on Self-Supporting Semiconducting Composite Film of Silicon Micro-Particles and Nano-Fibrillated Cellulose. Scientific Reports, 6(28921)
Open this publication in new window or tab >>Flexible Lamination-Fabricated Ultra-High Frequency Diodes Based on Self-Supporting Semiconducting Composite Film of Silicon Micro-Particles and Nano-Fibrillated Cellulose
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2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, no 28921Article in journal (Refereed) Published
Abstract [en]

Low cost and flexible devices such as wearable electronics, e-labels and distributed sensors will make the future "internet of things" viable. To power and communicate with such systems, high frequency rectifiers are crucial components. We present a simple method to manufacture flexible diodes, operating at GHz frequencies, based on self-adhesive composite films of silicon micro-particles (Si-mu Ps) and glycerol dispersed in nanofibrillated cellulose (NFC). NFC, Si-mu Ps and glycerol are mixed in a water suspension, forming a self-supporting nanocellulose-silicon composite film after drying. This film is cut and laminated between a flexible pre-patterned Al bottom electrode and a conductive Ni-coated carbon tape top contact. A Schottky junction is established between the Al electrode and the Si-mu Ps. The resulting flexible diodes show current levels on the order of mA for an area of 2 mm(2), a current rectification ratio up to 4 x 10(3) between 1 and 2 V bias and a cut-off frequency of 1.8 GHz. Energy harvesting experiments have been demonstrated using resistors as the load at 900 MHz and 1.8 GHz. The diode stack can be delaminated away from the Al electrode and then later on be transferred and reconfigured to another substrate. This provides us with reconfigurable GHz-operating diode circuits.

Place, publisher, year, edition, pages
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:liu:diva-130275 (URN)10.1038/srep28921 (DOI)000378907900001 ()27357006 (PubMedID)

Funding Agencies|Knut and Alice Wallenberg Foundation; Swedish Foundation for Strategic Research; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]

Available from: 2016-08-01 Created: 2016-07-28 Last updated: 2017-11-28
Toss, H., Sani, N., Fabiano, S., Simon, D. T., Forchheimer, R. & Berggren, M. (2016). Polarization of ferroelectric films through electrolyte. Journal of Physics: Condensed Matter, 28(10), Article ID 105901.
Open this publication in new window or tab >>Polarization of ferroelectric films through electrolyte
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2016 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 28, no 10, article id 105901Article in journal (Refereed) Published
Abstract [en]

A simplified model is developed to understand the field and potential distribution through devices based on a ferroelectric film in direct contact with an electrolyte. Devices based on the ferroelectric polymer polyvinylidenefluoride-trifluoroethylene (PVDF-TrFE) were produced – in metalferroelectric-metal, metal-ferroelectric-dielectric-metal, and metal-ferroelectric-electrolyte-metal architectures – and used to test the model, and simulations based on the model and these fabricated devices were performed. From these simulations we find indication of progressive polarization of the films. Furthermore, the model implies that there is a relation between the separation of charge within the devices and the observed open circuit voltage. This relation is confirmed experimentally. The ability to polarize ferroelectric polymer films through aqueous electrolytes, combined with the strong correlation between the properties of the electrolyte double layer and the device potential, opens the door to a variety of new applications for ferroelectric technologies, e.g., regulation of cell culture growth and release, steering molecular self-assembly, or other large area applications requiring aqueous environments.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2016
National Category
Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:liu:diva-121802 (URN)10.1088/0953-8984/28/10/105901 (DOI)000371007800015 ()

Funding agencies:  Swedish Governmental Agency for Innovation Systems (VINNOVA) [2010-00507]; Knut and Alice Wallenberg Foundation; Advanced Functional Materials Center at Linkoping University; Onnesjo Foundation

Available from: 2015-10-07 Created: 2015-10-07 Last updated: 2017-12-01Bibliographically approved
Abdollahi Sani, N., Robertsson, M., Cooper, P., Wang, X., Svensson, M., Andersson Ersman, P., . . . Gustafsson, G. (2014). All-printed diode operating at 1.6 GHz. Proceedings of the National Academy of Sciences of the United States of America, 111(33), 11943-11948
Open this publication in new window or tab >>All-printed diode operating at 1.6 GHz
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2014 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 111, no 33, p. 11943-11948Article in journal (Refereed) Published
Abstract [en]

Printed electronics are considered for wireless electronic tags and sensors within the future Internet-of-things (IoT) concept. As a consequence of the low charge carrier mobility of present printable organic and inorganic semiconductors, the operational frequency of printed rectifiers is not high enough to enable direct communication and powering between mobile phones and printed e-tags. Here, we report an all-printed diode operating up to 1.6 GHz. The device, based on two stacked layers of Si and NbSi2 particles, is manufactured on a flexible substrate at low temperature and in ambient atmosphere. The high charge carrier mobility of the Si microparticles allows device operation to occur in the charge injection-limited regime. The asymmetry of the oxide layers in the resulting device stack leads to rectification of tunneling current. Printed diodes were combined with antennas and electrochromic displays to form an all-printed e-tag. The harvested signal from a Global System for Mobile Communications mobile phone was used to update the display. Our findings demonstrate a new communication pathway for printed electronics within IoT applications.

Place, publisher, year, edition, pages
National Academy of Sciences, 2014
UHF; silicon particle
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Physical Sciences
urn:nbn:se:liu:diva-110476 (URN)10.1073/pnas.1401676111 (DOI)000340438800027 ()25002504 (PubMedID)

Funding Agencies|Knut and Alice Wallenberg Foundation (Power Paper Project) [KAW 2011.0050]; Onnesjo Foundation; Swedish Research Council Linnaeus Grant LiLi-NFM; European Regional Development Fund through Tillvaxtverket (Project PEA-PPP)

Available from: 2014-09-15 Created: 2014-09-12 Last updated: 2017-12-05Bibliographically approved

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