Device Strategies Directed to Improving the Efficiency of Solution-Processed Organic Solar Cells

Handle URI:
http://hdl.handle.net/10754/627733
Title:
Device Strategies Directed to Improving the Efficiency of Solution-Processed Organic Solar Cells
Authors:
Liang, Ru-Ze ( 0000-0002-1732-6133 )
Abstract:
In the last decade, organic photovoltaics (OPVs) have been attracting much attention for their low cost, and feasibility of mass production in large-area modules. Reported power conversion efficiencies (PCE) of organic solar cells have reached more than 10%. These promising PCEs can be realized by uncovering important principles: (1) rational molecular design, (2) matching of the material energy level, (3) favorable morphology of donor-acceptor (D/A) network, (4) higher carrier mobilities, and (5) suppression of charge recombination within the bulk heterojunction (BHJ). Though these key properties are frequently stated, the relationships between these principles remain unclear, which motivates us to fill these gaps. In the beginning, we show that changing the sequence of donor and acceptor units of the benzodithiophene-core (BDT) SM donors critically impacts molecular packing and charge transport in BHJ solar cells. Moreover, we find out that by adding small amount of the external solvent additive, the domain size of the SMFQ1 become relatively smaller, resulting in the FF enhancement of ~70% and thus pushing PCE to >6.5%. To further improve the device performance, we utilize another technique of device optimization: Solvent Vapor Annealing (SVA). Compared with solvent additive, the SVA creates a solvent-saturated environment for SMs to re-arrange and crystalize, leading to PCE of >8%, with nearly-free bimolecular recombination. When the systems are shifted from fullerene acceptors to nonfullerene acceptors, using solvent additives in indacenodithiophene-core (IDT) systems significantly reduces the domain size from >500nm to <50nm and also allows the SM donors to orderly packed, rising the PCE from <1% to 4.5%. Furthermore in a similar IDT-based system, it shows unexpectedly high VOC and low energy loss, and high PCE > 6% can be reached by employing the dimethyl disulfide (DMDS) as the SVA solvent to re-organize the morphology from excessive mixing to ordered phase-separated D/A network. Lastly, taking advantage of the distinct and complementary absorption of fullerene and nonfullerene acceptors, we show that the SM ternary system successfully realizes the high PCE of 11%, good air stability, and scalable property.
Advisors:
Beaujuge, Pierre ( 0000-0003-2868-4494 )
Committee Member:
Alshareef, Husam N. ( 0000-0001-5029-2142 ) ; He, Jr-Hau ( 0000-0003-1886-9241 ) ; Jones, David J.
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Program:
Materials Science and Engineering
Issue Date:
18-Apr-2018
Type:
Dissertation
Appears in Collections:
Dissertations

Full metadata record

DC FieldValue Language
dc.contributor.advisorBeaujuge, Pierreen
dc.contributor.authorLiang, Ru-Zeen
dc.date.accessioned2018-05-01T13:50:52Z-
dc.date.available2018-05-01T13:50:52Z-
dc.date.issued2018-04-18-
dc.identifier.urihttp://hdl.handle.net/10754/627733-
dc.description.abstractIn the last decade, organic photovoltaics (OPVs) have been attracting much attention for their low cost, and feasibility of mass production in large-area modules. Reported power conversion efficiencies (PCE) of organic solar cells have reached more than 10%. These promising PCEs can be realized by uncovering important principles: (1) rational molecular design, (2) matching of the material energy level, (3) favorable morphology of donor-acceptor (D/A) network, (4) higher carrier mobilities, and (5) suppression of charge recombination within the bulk heterojunction (BHJ). Though these key properties are frequently stated, the relationships between these principles remain unclear, which motivates us to fill these gaps. In the beginning, we show that changing the sequence of donor and acceptor units of the benzodithiophene-core (BDT) SM donors critically impacts molecular packing and charge transport in BHJ solar cells. Moreover, we find out that by adding small amount of the external solvent additive, the domain size of the SMFQ1 become relatively smaller, resulting in the FF enhancement of ~70% and thus pushing PCE to >6.5%. To further improve the device performance, we utilize another technique of device optimization: Solvent Vapor Annealing (SVA). Compared with solvent additive, the SVA creates a solvent-saturated environment for SMs to re-arrange and crystalize, leading to PCE of >8%, with nearly-free bimolecular recombination. When the systems are shifted from fullerene acceptors to nonfullerene acceptors, using solvent additives in indacenodithiophene-core (IDT) systems significantly reduces the domain size from >500nm to <50nm and also allows the SM donors to orderly packed, rising the PCE from <1% to 4.5%. Furthermore in a similar IDT-based system, it shows unexpectedly high VOC and low energy loss, and high PCE > 6% can be reached by employing the dimethyl disulfide (DMDS) as the SVA solvent to re-organize the morphology from excessive mixing to ordered phase-separated D/A network. Lastly, taking advantage of the distinct and complementary absorption of fullerene and nonfullerene acceptors, we show that the SM ternary system successfully realizes the high PCE of 11%, good air stability, and scalable property.en
dc.language.isoenen
dc.subjectOrganic Solar Cellen
dc.subjectFullereneen
dc.subjectSmall Moleculeen
dc.subjectPhotovoltaicen
dc.subjectBulk heterojunctionen
dc.titleDevice Strategies Directed to Improving the Efficiency of Solution-Processed Organic Solar Cellsen
dc.typeDissertationen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen
dc.contributor.committeememberAlshareef, Husam N.en
dc.contributor.committeememberHe, Jr-Hauen
dc.contributor.committeememberJones, David J.en
thesis.degree.disciplineMaterials Science and Engineeringen
thesis.degree.nameDoctor of Philosophyen
dc.person.id130759en
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