@article{TurnerPingelSteyrleuthneretal.2011, author = {Turner, Sarah T. and Pingel, Patrick and Steyrleuthner, Robert and Crossland, Edward J. W. and Ludwigs, Sabine and Neher, Dieter}, title = {Quantitative analysis of bulk heterojunction films using linear absorption spectroscopy and solar cell performance}, series = {Advanced functional materials}, volume = {21}, journal = {Advanced functional materials}, number = {24}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1616-301X}, doi = {10.1002/adfm.201101583}, pages = {4640 -- 4652}, year = {2011}, abstract = {A fundamental understanding of the relationship between the bulk morphology and device performance is required for the further development of bulk heterojunction organic solar cells. Here, non-optimized (chloroform cast) and nearly optimized (solvent-annealed o-dichlorobenzene cast) P3HT:PCBM blend films treated over a range of annealing temperatures are studied via optical and photovoltaic device measurements. Parameters related to the P3HT aggregate morphology in the blend are obtained through a recently established analytical model developed by F. C. Spano for the absorption of weakly interacting H-aggregates. Thermally induced changes are related to the glass transition range of the blend. In the chloroform prepared devices, the improvement in device efficiency upon annealing within the glass transition range can be attributed to the growth of P3HT aggregates, an overall increase in the percentage of chain crystallinity, and a concurrent increase in the hole mobilities. Films treated above the glass transition range show an increase in efficiency and fill factor not only associated with the change in chain crystallinity, but also with a decrease in the energetic disorder. On the other hand, the properties of the P3HT phase in the solvent-annealed o-dichlorobenzene cast blends are almost indistinguishable from those of the corresponding pristine P3HT layer and are only weakly affected by thermal annealing. Apparently, slow drying of the blend allows the P3HT chains to crystallize into large domains with low degrees of intra- and interchain disorder. This morphology appears to be most favorable for the efficient generation and extraction of charges.}, language = {en} } @phdthesis{Yin2009, author = {Yin, Chunhong}, title = {The interplay of nanostructure and efficiency of polymer solar cells}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-29054}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {The aim of this thesis is to achieve a deep understanding of the working mechanism of polymer based solar cells and to improve the device performance. Two types of the polymer based solar cells are studied here: all-polymer solar cells comprising macromolecular donors and acceptors based on poly(p-phenylene vinylene) and hybrid cells comprising a PPV copolymer in combination with a novel small molecule electron acceptor. To understand the interplay between morphology and photovoltaic properties in all-polymer devices, I compared the photocurrent characteristics and excited state properties of bilayer and blend devices with different nano-morphology, which was fine tuned by using solvents with different boiling points. The main conclusion from these complementary measurements was that the performance-limiting step is the field-dependent generation of free charge carriers, while bimolecular recombination and charge extraction do not compromise device performance. These findings imply that the proper design of the donor-acceptor heterojunction is of major importance towards the goal of high photovoltaic efficiencies. Regarding polymer-small molecular hybrid solar cells I combined the hole-transporting polymer M3EH-PPV with a novel Vinazene-based electron acceptor. This molecule can be either deposited from solution or by thermal evaporation, allowing for a large variety of layer architectures to be realized. I then demonstrated that the layer architecture has a large influence on the photovoltaic properties. Solar cells with very high fill factors of up to 57 \% and an open circuit voltage of 1V could be achieved by realizing a sharp and well-defined donor-acceptor heterojunction. In the past, fill factors exceeding 50 \% have only been observed for polymers in combination with soluble fullerene-derivatives or nanocrystalline inorganic semiconductors as the electron-accepting component. The finding that proper processing of polymer-vinazene devices leads to similar high values is a major step towards the design of efficient polymer-based solar cells.}, language = {en} } @phdthesis{Trommer2001, author = {Trommer, Jochen}, title = {Distributed optimality}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001377}, school = {Universit{\"a}t Potsdam}, year = {2001}, abstract = {In dieser Dissertation schlage ich eine Synthese (Distributed Optimality, DO) von Optimalit{\"a}tstheorie und einem derivationellen, morphologischem Asatz, Distributed Morphology (DM; Halle \& Marantz, 1993) vor. Durch die Integration von OT in DM wird es m{\"o}glich, Ph{\"a}nomene, die in DM durch sprachspezifische Regeln oder Merkmale von lexikalischen Eintr{\"a}ge erfasst werden, auf die Interaktion von verletzbaren, universellen Constraints zur{\"u}ckzuf{\"u}hren. Andererseits leistet auch DM zwei substantielle Beitr{\"a}ge zu DO, Lokalit{\"a}t und Impoverishment. Lokalit{\"a}t erlaubt eine formal einfache Interpretation von DO, w{\"a}hrend sich Impoverishment als unverzichtbar erweist, um Kongruenz-Morphologie ad{\"a}quat zu beschreiben. Die empirische Grundlage der Arbeit sind die komplexen Kongruenzsysteme von genetisch unterschiedlichen Sprachen. Der theoretische Schwerpunkt liegt in zwei Bereichen: Erstens, sogenannte Direkt/Invers-Markierung, f{\"u}r die gezeigt wird, dass eine Behandlung durch Constraints {\"u}ber Merkmalsrealisierung am angemessensten ist. Zweitens, die Effekte von Abfolge-Constraints, die den Satus von Affixen als Pr{\"a}fixe und Suffixe sowie ihre relative Reihenfolge regeln. Eine konkrete Typologie f{\"u}r die Abfolge von Kongruenz-Affixen auf der Basis von OT-Constraints wird vorgeschlagen.}, language = {en} } @phdthesis{Kukula2001, author = {Kukula, Hildegard}, title = {Lineare und verzweigte Blockcopolymere aus Polypeptiden und synthetischen Polymeren}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0000040}, school = {Universit{\"a}t Potsdam}, year = {2001}, abstract = {Die vorliegende Arbeit besch{\"a}ftigt sich mit der Synthese und den Eigenschaften von linearen und verzweigten amphiphilen Polypeptid-Blockcopolymeren. Die Frage nach dem Einfluss der Topologie und Konformation der Blockcopolymere auf die supramolekularen und kolloidalen Eigenschaften bildete einen wichtigen Aspekt bei den Untersuchungen. Die Blockcopolymere wurden nach einem mehrstufigen Reaktionsschema durch Kombination von anionischer und ring{\"o}ffnender Polymerisation von Aminos{\"a}uren-N-Carboxyanhydriden (NCA) synthetisiert. Die Untersuchung der Polypeptid-Blockcopolymere hinsichtlich ihres Aggregationsverhaltens in fester Phase sowie in verd{\"u}nnter w{\"a}ssriger L{\"o}sung erfolgte mittels Streumethoden (SAXS, WAXS, DLS) sowie abbildender Methoden (TEM). Durch Einsatz der Blockcopolymere als polymere Stabilisatoren in der Emulsionspolymerisation wurden Oberfl{\"a}chen funktionalisierte Latizes erhalten. Als Beispiel f{\"u}r eine pharmazeutische Anwendung wurden biovertr{\"a}gliche Polypeptid-Blockcopolymere als Wirkstoff-Tr{\"a}gersysteme in der Krebstherapie eingesetzt.}, language = {de} }