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Polymer/polymer blends in organic photovoltaic and photodiode devices
Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
2018 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Organic photovoltaics devices (OPV) have attracted attentions of scientist for their potential as inexpensive, lightweight, flexible and suitable for roll-to-roll production. In recent years, considerable attention has been focused on new acceptor materials, either polymeric or small molecules, to replace the once dominating fullerene derivatives. The emergence of numerous new non-fullerene materials has driven power conversion efficiency (PCE) up to 17%, attracting more and more interests of commercialization.

Polymer acceptors with more morphology stability, more absorption and more desired energy levels has been intensively studied and show great potential for large area and low-cost production in the future. OPV at this moment is not yet competitive with inorganic solar cells in PCE but is more attractive in flexibility, low weight and semitransparency. In this thesis, some basic knowledges of OPV is introduced in the first few chapters, while the next chapters are focusing on polymer-polymer blends and investigating novel structures and techniques for large scale production of solar cells and photodetectors aiming at maximizing these advantages to compete with inorganic counterpart.

Thermal annealing effects on polymer-polymer solar cells based is studied. Annealed devices show doubled power conversion efficiency compared to non-annealed devices. Based on the morphology—mobility examination, we conclude that the better charge transport is achieved by higher order and better interconnected networks of the bulk heterojunction in the annealed active layers. The annealing improves charge transport and extends the conjugation length of the polymers, which do help charge generation and meanwhile reduce recombination. The blend of an amorphous polymer and a semi-crystalline polymer can thus be modified by thermal annealing to double the power conversion efficiency.

A novel concept of all-polymer organic photovoltaics device is demonstrated in this thesis where all the layers are made out of polymers. We use PEDOT:PSS as semitransparent anode and polyethyleneimine modified PEDOT:PSS as semitransparent cathode, both of which are slot-die printed on polyethylene terephthalate(PET). Active layers are deposited on cathode and anode surfaces by spin coating separately. These layers are then joined through a roll-to-roll compatible lamination process. This forms a semitransparent and flexible solar cell. By laminating a thin layer acceptor polymer to a thick polymer-polymer blend, we can further improve the performance by reducing traps comparing to laminating blend to blend.

Flexible and semitransparent all-polymer photodiodes with different geometries can be fabricated through lamination. By choosing high band gap polymers and appropriate combination of two or more polymers, organic photodiode with low noise and high specific detectivity can be obtained. Comparison between bilayer and bulk heterojunction devices gives better understanding of the origin of noise and provides ways to improve the performance of photodiodes as detector.

Noise level is a critical parameter for photodetectors. The difficulties of measuring the noise of photodetectors make some researchers prefer the estimated shot noise as the dominating one and ignore the thermal noise and 1/f noise. The latter two terms are sometimes several orders higher than the former, noting the importance of experimentally measuring noise.

The use of semi-transparent photovoltaic devices causes an inevitable loss of photocurrent, as light transmitted has not been absorbed. This trivial effect also leads to a loss of photovoltage, an effect partially due to the lower photocurrent but also due to the geometry of the semitransparent photovoltaic device. We here demonstrate and evaluate this photovoltage loss in semi-transparent organic photovoltaic devices, compared with non-transparent solar cells of the same material. Semi-transparent solar cells in addition introduce photovoltage loss when formed by lamination. We document and analyze these effects for a number of polymer blends in the form of bulk heterojunctions.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2018. , s. 60
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1974
Nationell ämneskategori
Polymerkemi Polymerteknologi Materialkemi
Identifikatorer
URN: urn:nbn:se:liu:diva-153616DOI: 10.3384/diss.diva-153616ISBN: 9789176851463 (tryckt)OAI: oai:DiVA.org:liu-153616DiVA, id: diva2:1274981
Disputation
2019-01-18, Planck, Fysikhouset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2019-01-04 Skapad: 2019-01-04 Senast uppdaterad: 2019-01-04Bibliografiskt granskad
Delarbeten
1. Inverted all-polymer solar cells based on a quinoxaline-thiophene/naphthalene-diimide polymer blend improved by annealing
Öppna denna publikation i ny flik eller fönster >>Inverted all-polymer solar cells based on a quinoxaline-thiophene/naphthalene-diimide polymer blend improved by annealing
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2016 (Engelska)Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, nr 10, s. 3835-3843Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We have investigated the effect of thermal annealing on the photovoltaic parameters of all-polymer solar cells based on a quinoxaline-thiophene donor polymer (TQ1) and a naphthalene diimide acceptor polymer (N2200). The annealed devices show a doubled power conversion efficiency compared to nonannealed devices, due to the higher short-circuit current (J(sc)) and fill factor (FF), but with a lower open circuit voltage (V-oc). On the basis of the morphology-mobility examination by several scanning force microscopy techniques, and by grazing-incidence wide-angle X-ray scattering, we conclude that better charge transport is achieved by higher order and better interconnected networks of the bulk heterojunction in the annealed active layers. The annealing improves charge transport and extends the conjugation length of the polymers, which do help in charge generation and meanwhile reduce recombination. Photoluminescence, electroluminescence, and light intensity dependence measurements reveal how this morphological change affects charge generation and recombination. As a result, the J(sc) and FF are significantly improved. However, the smaller band gap and the higher HOMO level of TQ1 upon annealing causes a lower V-oc. The blend of an amorphous polymer TQ1, and a semi-crystalline polymer N2200, can thus be modified by thermal annealing to double the power conversion efficiency.

Ort, förlag, år, upplaga, sidor
ROYAL SOC CHEMISTRY, 2016
Nationell ämneskategori
Biologiska vetenskaper
Identifikatorer
urn:nbn:se:liu:diva-127066 (URN)10.1039/c6ta00531d (DOI)000371967000030 ()
Anmärkning

Funding Agencies|Swedish Energy Agency; Swedish Research council, NSFC [21504006, 21534003]; Knut and Alice Wallenberg Foundation through a Wallenberg scholar grant; China Scholarship Council (CSC); graduate student short-term abroad research project of Jinan University; program for the Excellent Doctoral Dissertations of Guangdong Province [ybzzxm201114]; U.S. Department of Energy [DE-AC02-05CH11231]

Tillgänglig från: 2016-04-13 Skapad: 2016-04-13 Senast uppdaterad: 2019-01-04
2. Semitransparent all-polymer solar cells through lamination
Öppna denna publikation i ny flik eller fönster >>Semitransparent all-polymer solar cells through lamination
2018 (Engelska)Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, nr 42, s. 21186-21192Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

In this work, we demonstrate all-polymer solar cells where all the layers are made from polymers. We use PEDOT:PSS as the semitransparent anode and polyethyleneimine modified PEDOT:PSS as the semitransparent cathode, both of which are slot-die printed on polyethylene terephthalate (PET). Active layers are deposited on the cathode and anode surfaces by spin coating separately. These layers are then joined through a roll-to-roll compatible lamination process. This results in a semitransparent and flexible solar cell. We have used two polymer-polymer systems and several combinations, and the highest power conversion efficiency (PCE) obtained is 2.3% with a mean transparency amp;gt;35% within the visible light range. By laminating a thin layer acceptor polymer to a thick polymer-polymer blend, we can improve the performance by reducing recombination, compared to laminating blend to blend, which is verified by the trap-limited charge transport, CELIV and electroluminescence.

Ort, förlag, år, upplaga, sidor
ROYAL SOC CHEMISTRY, 2018
Nationell ämneskategori
Polymerkemi
Identifikatorer
urn:nbn:se:liu:diva-153535 (URN)10.1039/c8ta07992g (DOI)000451600200066 ()
Anmärkning

Funding Agencies|Swedish Energy Agency; Knut and Alice Wallenberg foundation (KAW); China Scholarship Council (CSC)

Tillgänglig från: 2018-12-20 Skapad: 2018-12-20 Senast uppdaterad: 2019-03-25
3. Large-Area, Semitransparent, and Flexible All-Polymer Photodetectors
Öppna denna publikation i ny flik eller fönster >>Large-Area, Semitransparent, and Flexible All-Polymer Photodetectors
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2018 (Engelska)Ingår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, nr 48, artikel-id 1805570Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Photodetectors, converting optical signals from specific wavelengths to electrical signals, have many applications on photoimaging, optical communication, and environmental monitoring. Solution-processed organic photodetectors (OPDs) based on organic materials emerge promise especially for wearable electronics and smart buildings. In this work, new all-polymer photodetectors (all-PPDs) are developed based on bulk-heterojunction active layers which incorporate a donor polymer and an acceptor polymer. The inverted all-PPDs exhibit outstanding external quantum efficiency over 70%, low dark current density (J(d)) of 1.1 x 10(-8) A cm(-2), and high detectivity (D*) over 3.0 x 10(12) Jones with planar response over the entire visible range. It is one of the best-performing all-PPDs reported so far and is also comparable with many organic and inorganic photodetectors. By using lamination technique, large-area, semitransparent, flexible, and "fully" polymeric photodetectors are successfully fabricated for the first time, with D* over 10(11) Jones for double-side light detection. The results highlight the great potential for producing high-performance all-PPDs by taking advantages of various device architecture and solution-processing techniques.

Ort, förlag, år, upplaga, sidor
WILEY-V C H VERLAG GMBH, 2018
Nyckelord
all-polymer photodetectors; conjugated polymers; flexible electronics; semitransparent electronics
Nationell ämneskategori
Materialkemi
Identifikatorer
urn:nbn:se:liu:diva-153367 (URN)10.1002/adfm.201805570 (DOI)000451118800014 ()
Anmärkning

Funding Agencies|Knut and Alice Wallenberg foundation through a Wallenberg Scholar grant; Ocean University of China; Ministry of Science and Technology [2016YFA0200700]; National Natural Science Foundation of China [21704082, 21875182, 21534003, 51320105014]; China Postdoctoral Science Foundation [2017M623162]; Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy [DE-AC02-05CH11231]; China Scholarship Council (CSC)

Tillgänglig från: 2018-12-18 Skapad: 2018-12-18 Senast uppdaterad: 2019-01-04

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