THESIS
2019
xv, 111, that is, xvi, 115 pages : illustrations ; 30 cm
Abstract
Organic Solar Cells have been attracting attentions from both academia and industry
owing to its reduced fabrication cost, light weight and mechanical flexibility. Rational
material design and feasible synthetic routes are critical to realize the solar cell
technology in real-life applications, though the morphological control, the structure-property
relationship, synthetic methodology are not yet fully explored. Thus in this
thesis, I will show my efforts in developing novel donor and acceptor materials with
good performance and good stability.
To approach high efficiencies in device, one of the critical pathway is to achieve an
ideal morphology in blend film. Based on the temperature-dependent-aggregation
strategy, we developed a novel low bandgap polymer PffBTT2-DPPT2, which...[
Read more ]
Organic Solar Cells have been attracting attentions from both academia and industry
owing to its reduced fabrication cost, light weight and mechanical flexibility. Rational
material design and feasible synthetic routes are critical to realize the solar cell
technology in real-life applications, though the morphological control, the structure-property
relationship, synthetic methodology are not yet fully explored. Thus in this
thesis, I will show my efforts in developing novel donor and acceptor materials with
good performance and good stability.
To approach high efficiencies in device, one of the critical pathway is to achieve an
ideal morphology in blend film. Based on the temperature-dependent-aggregation
strategy, we developed a novel low bandgap polymer PffBTT2-DPPT2, which contains
a D-A1-D-A2 structure. With the introduction of a second electron-withdrawing unit,
ffBT, PffBTT2-DPPT2 possessed a much deeper HOMO energy level and stronger
temperature-dependent aggregation property than its analogue PDPP4T, resulting in an
enhanced Voc as well as PCE up to 8.6%. Owing to its deeper energy levels as well as
stronger aggregation property, PffBTT2-DPPT2 based devices possessed excellent
stability, not only in air stability and thermal stability, but also in light-soaking stability.
Over 80% of PCE maintained after being illuminated under light for 283h.
An environmental-friendly method to synthesis the photo-active materials is of vital
important to bringing organic solar cells into real-life application. We developed a novel
large band-gap polymer PFFTAZ-4FTVT with direct hetero-arylation polymerization
method, which was more straightforward and would not generate any toxic
organometallic compound. Synthetic methods were detailed explored, including
temperature selection, solvent selection and etc. Mesitylene stood out owing to the
excellent dissolving ability both monomers and the resulting polymers as well as less
reactivity in the polymerization process. The temperature-depend aggregation strategy
was also applied to the polymer design to achieve an ideal blend-film morphology, as a
result, the devices based on PFFTAZ-4FTVT:PC
71BM achieved a good PCE of 6.91%.
To achieve fine-tune energy levels as well as stronger absorption, small molecular
acceptors (SMA) was greatly developed. However, the molecular ordering in SMA
based systems are not yet fully understood. We developed a novel small molecular
acceptor TS-5 by replacing the benzene ring in the ending group with thiophene ring.
The resulting molecular exhibited a clear hypsochromatic shift in either solution and
solid state once diiodooctane was applied. By tuning the molecular packing, a
significant enhancement of Voc (0.1V enhancement) was achieved without any
negative impact on the overall PCE. This is the first report of this unique phenomenon
in organic solar cells.
Post a Comment