THESIS
2022
1 online resource (xx, 133 pages) : illustrations (chiefly color)
Abstract
Organic solar cell (OSC) is one of the most promising third-generation solar cell technologies
as organic solar modules are flexible, lightweight and semi-transparent, which can be produced
by high-throughput roll-to-roll (R2R) printing processes. Indeed, the past few years have
witnessed a significant advance in efficiency of non-fullerene acceptor (NFA) OSCs, which
benefits from the emergence of outstanding materials. In this thesis, my research work focuses
on designing and synthesizing donor and acceptor materials for achieving high-performance
solar cells, paving a way for understanding the effect of molecular structures on morphological
behaviour and device performance.
Chapter I introduces the background of OSCs, including the device types, photoelectric
conversion mechanism, pho...[
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Organic solar cell (OSC) is one of the most promising third-generation solar cell technologies
as organic solar modules are flexible, lightweight and semi-transparent, which can be produced
by high-throughput roll-to-roll (R2R) printing processes. Indeed, the past few years have
witnessed a significant advance in efficiency of non-fullerene acceptor (NFA) OSCs, which
benefits from the emergence of outstanding materials. In this thesis, my research work focuses
on designing and synthesizing donor and acceptor materials for achieving high-performance
solar cells, paving a way for understanding the effect of molecular structures on morphological
behaviour and device performance.
Chapter I introduces the background of OSCs, including the device types, photoelectric
conversion mechanism, photovoltaic parameters, molecular properties, morphological
characterization and morphological optimization. Additionally, recent progress of OSC
materials is summarized, especially the Y-type NFAs which are important stimulation for the
development of OSCs.
Chapter II presents the random polymerization strategy to produce a series of terpolymers with
various energy levels while maintain well-controlled morphology. These random copolymers
are based on D-A1-D-A2 backbone of which the D and A1 units are building blocks from PM6 or PM7 while the A2 unit consists of an electron-poor core flanked by two thiophenes with 2-
ethylhexyl chains. As a result, these random polymers yielded multiple high-performance OSCs
with PCEs ranging from 16% to 17.1%. Indeed, there are a lot of moieties with other chemical
structures that can serve as the A2 unit, which can produce many other polymers to match with
different NFAs and fulfil their potential.
In Chapter III, we combined branched alkyl chain strategy and alkoxy chain strategy to
develop a high-performance NFA based on the conjugated skeleton of Y6. The resulting
molecule named Y6-O2BO demonstrated a much enhanced Voc of 0.96 V and highly ordered
molecular packing pattern in the blend film, compared to the previously used branched alkyl or
linear alkoxy modifications. It is noteworthy that Y6-O2BO exhibits an orderly molecular
stacking and small π-π stacking distance in blend film, which could benefit for charge transport
of device. The successfully synergistic modulation of the morphological and photovoltaic
performance for NFA indicates that branched alkoxy chain is a promising strategy to design
high-performance NFAs and thus accelerate the development of OSCs.
Chapter IV summarizes the content of this thesis and explores the challenges OSCs will
confront in the future from the perspective of practical application in industry.
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