THESIS
2021
1 online resource (xix, 177 pages) : illustrations (some color)
Abstract
Organic solar cells (OSCs) are an attractive technology due to the advantages of low production
cost, mechanical flexibility and compatibility with roll-to-roll printing. Recent advances in
small molecular acceptors (SMAs) and all-polymer solar cells (all-PSCs) have brought a
“paradigm shift” from fullerene devices to non-fullerene devices. However, the structure-property relationships and donor-acceptor interactions according to morphological and
photophysical aspects are still not clear enough. In this thesis, I will introduce my research
focused on the molecular design of small molecule and polymer acceptor materials aiming to
provide comprehensions into highly efficient non-fullerene OSCs.
Chapter II
highlights the strategy of fluorination on end group moieties for high-performance...[
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Organic solar cells (OSCs) are an attractive technology due to the advantages of low production
cost, mechanical flexibility and compatibility with roll-to-roll printing. Recent advances in
small molecular acceptors (SMAs) and all-polymer solar cells (all-PSCs) have brought a
“paradigm shift” from fullerene devices to non-fullerene devices. However, the structure-property relationships and donor-acceptor interactions according to morphological and
photophysical aspects are still not clear enough. In this thesis, I will introduce my research
focused on the molecular design of small molecule and polymer acceptor materials aiming to
provide comprehensions into highly efficient non-fullerene OSCs.
Chapter II
highlights the strategy of fluorination on end group moieties for high-performance
polymer acceptors thus promoting efficiencies of all-PSCs. Three examples of my research
work on all-PSCs are summarized, including: 1) fluorinated end group on polymer acceptors
enable all-PSCs with red-shifted absorption; 2) regio-regular polymer acceptors enabled by
determined fluorination on end groups for all PSCs; 3) a difluoro-monobromo end group
enables superior polymer acceptors for high-performance all-PSCs. Systematic study among a
series of polymer acceptors is made regarding optoelectronic properties, device performances,
photophysics and morphology. Record efficiencies of up to 17% are achieved despite of low
voltage losses of ~0.5 V for all PSCs.
Chapter III
concentrates on enhancing intramolecular charge transfer (ICT) effect to promote
performances of Y-series SMAs via central molecule backbone modulation. One case is the introduction
of selenium-incorporated heterocycles with stronger electron-donating ability and quinoid propertiy, enabling red-shifted absorption and stronger intermolecular packing relative
to the orginal Y6 counterpart. The benzoselenathiazole substituted one exhibited stronger effect
and better device performance than the selenothiophene-substituted one, resulting an absorption
onset extended to ~950 nm and a efficienc over 16%.
Chapter IV investigates the structure-performance relationship for a pair of isomeric perylene-diimide (PDI) SMAs with a [2.2]paracyclophane core. Systematic comparisons are processed
regarding optoelectronic properties, device performances and morphology. The one with better
transannularly conjugation in molecule geometry exhibited a better efficiency over 9%.
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