Design, Synthesis and Modelling of Conjugated Polymers for Organic Photovoltaics
Doktorsavhandling, 2013

Secure, clean and renewable energy sources are believed to be the eventual solution for sustainable energy, especially by the direct utilization of solar energy. Organic photovoltaics offer such an option to convert solar energy into electricity based on solution-processed, lightweight, large-area, and potentially flexible devices. The current challenges for organic photovoltaics remain to further improve efficiency as well as durability and cost-effectiveness, to compete with traditional silicon-based solar cells. Material design through band gap and energy level tuning has been playing a key role in developing new donor materials for efficient polymer solar cells. Computationally driven material design can accelerate the search for optimal conjugated polymers, and the exploration of chemical methodologies is highly desirable in pushing the efficiency further toward the theoretical limit. This thesis deals with the design, synthesis, characterization, and computational modelling of π-conjugated polymers for bulk heterojunction organic solar cells. It focuses on material design of conjugated donor polymers through band gap and energy level engineering via structural modifications such as backbone manipulations, side-chain engineering, as well as incorporation of newly developed building blocks. This also establishes structure–property relationships of the polymer systems here studied, and explores potential chemical methodologies for future judicious material design.

computational modelling

energy level

material design

organic photovoltaics

conjugated polymers

band gap

structure–property relationships

KB-salen, Kemigården 4, Göteborg
Opponent: Prof. Dirk Vanderzande, Hasselt University, Belgium


Wenliu Zhuang

Chalmers, Kemi- och bioteknik, Polymerteknologi

Solceller samlar in solenergin och omvandlar den till elektricitet. De bästa solcellerna gjorda av kisel visar idag en effektivitet på ca 25 %. Dock är denna typ av solceller fortfarande för dyr för att konkurera med fossila bränslen och dessutom har även kiselindustrin en stor miljöpåverkan. Alternativa solcellstekniker är under utveckling. En av dessa bygger på specialdesignade polymerer, så kallade konjugerade polymerer. Polymerer är huvudkomponenten i plast som kan hittas nästan överallt i vardagen, t.ex. används de som isoleringsmaterial i elektriska kablar. Ledande polymerer upptäcktes 1977 och denna upptäckt belönades med nobelpriset i kemi 2000. Polymera solceller är en lovande applikation där dessa polymerer kommer absorbera ljus och omvandla det till elektricitet. Denna avhandling handlar om just detta; polymera solceller. Den behandlar design, syntes, utvärdering och modellering av konjugerade polymerer för användning i solceller så att de kan omvandla solenergin mer effektivt. Designen av konjugerade polymerer kan vara komplicerad och bygger på kunskap och erfarenhet, vilket betyder att många polymerer behövs syntetiseras och utvärderas för att nå en så hög effektivitet som möjligt. I samband med utvecklingen av datorvetenskap och teknologi, har det också utvecklats möjligheter att göra modelleringar vilket kan hjälpa till med designen av nya material. Det ultimata målet är att göra polymera solceller mer effektiva, mer hållbara och dessutom billigare.

Solar cells harness solar energy and convert it directly into electrical energy by the photovoltaic effect, which was discovered in 1839. The best efficiency of silicon solar cells to date is around 25%. However, they are still too expensive to compete with fossil fuels, apart from the serious environmental impact of the silicon industry. There are alternative solar cells technologies under development. One of them is based on specially designed plastics, so-called conjugated polymers. Polymers as the main component of plastics can be found almost everywhere in our everyday life, and they are typically insulators and may be used in power cables. In 1977, conductive polymers were discovered, and for this discovery three principal scientists won the Nobel Prize in Chemistry in 2000. Polymer solar cells are a promising application that absorb sunlight and convert it into electricity. This thesis is about polymer solar cells. It deals with design, synthesis, evaluation and modelling of conjugated polymers for use in solar cells to harvest solar energy more efficiently. The design of conjugated polymers can be quite complicated and relies on knowledge and experience. So a lot of polymers need to be synthesized and evaluated. However, with the development of computer science and technology, there is also computational modelling to aid design of materials. The ultimate aim is to make polymer solar cells more efficient, more durable, and cheaper.






C3SE (Chalmers Centre for Computational Science and Engineering)





Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 3634

KB-salen, Kemigården 4, Göteborg

Opponent: Prof. Dirk Vanderzande, Hasselt University, Belgium