Organic solar cells have great potential for cost-effective and large area electricity production, but their applicability is limited by the relatively low efficiency. In this dissertation I report investigations of novel materials and the underlying principles of organic solar cells, carried out at the University of St Andrews between 2011 and 2015. Key results of this investigation: • The charge carrier mobility of organic semiconductors in the active layer of polymer solar cells has a rather small influence on the power conversion efficiency. Cooling solar cells of the polymer:fullerene blend PTB7:PC₇₁BM from room temperature to 77 K decreased the hole mobility by a factor of thousand but the device efficiency only halved. • Subphthalocyanine molecules, which are commonly used as electron donor materials in vacuum-deposited active layers of organic solar cells, can, by a slight structural modification, also be used as efficient electron acceptor materials in solution-deposited active layers. Additionally these acceptors offer, compared to standard fullerene acceptors,advantages of a stronger light absorption at the peak of the solar spectrum. • A low band-gap polymer donor material requires a careful selection of the acceptor material in order to achieve efficient charge separation and a maximum open circuit voltage. • Metal structures in nanometer-size can efficiently enhance the electric field and light absorption in organic semiconductors by plasmonic resonance. The fluorescence of a P3HT polymer film above silver nanowires, separated by PEDOT:PSS, increased by factor of two. This could be clearly assigned to an enhanced absorption as the radiative transition of P3HT was identical beside the nanowires. • The use of a processing additive in the casting solution for the active layer of organic solar cells of PTB7:PC₇₁BM strongly influences the morphology, which leads not only to an optimum of charge separation but also to optimal charge collection.

The present thesis is focused on rational design and synthesis of π-conjugated donor-acceptor (D-A) type oligomers and polymers. It is organized in six different chapters and a brief discussion on the content of the individual chapter is provided below. Chapter 1 briefly describes the charge transport properties of organic semiconductors followed by recent development of different organic semiconducting materials mainly for applications in OFET and solar cells have been highlighted. Chapter 2 explores the synthesis and characterization of two new liquid crystalline, D-A type bithiophene-benzothiazole derivatives. The liquid crystalline properties of the materials have been studied in detail with optical polarizing microscopic images and differential scanning calorimetry and found that these materials possess highly ordered smectic A liquid crystalline phase. Their charge transport properties have also been investigated by fabricating OFET devices. Chapter 3 describes the photophysical properties and OFET performance of quinoxaline based donors-acceptor-donor (D-A-D) type molecules. Depending on the flexibility and rigidity of the conjugated backbone these materials show liquid crystalline behaviour. Investigation of their OFET performance indicated that these molecules exhibit p-type mobility up to 9.7 x 10-4 cm2V-1s-1 and on/ off ratio of 104. Chapter 4 investigates excited state properties and OFET behavior of D-A-D type diketopyrrolopyrrole (DPP) derivatives end-capped with alkoxynaphthalene group. UV-Visible spectroscopy measurement shows strong intramolecular charge transfer (ICT) between donor and acceptor unit. Steady-state and time-resolved fluorescence measurements confirm the formation of excimer. The excited state interactions, the interchromophore separation and geometry of the molecules influence the extent of excimer formation. Finally, the OFET behavior of these DPP based materials has been studied using different dielectric layers. Chapter 5 discusses the synthesis, characterization and properties of two new thieno[3,2-b]thiophene-DPP based donor-acceptor (D-A) type low band gap polymers (PTTDPP-BDT and PTTDPP-BZT). Investigation of OFET performance indicated that polymers exhibited ambipolar behaviour with hole mobility upto 1.0 x 10-3 cm2/Vs and electron mobility upto 8 x 10-5 cm2/Vs. Using polymer PTTDPP-BDT with electron acceptor C70PCBM, power conversion efficiency (PCE) around 3.26% in bulk heterojunction solar cell has been achieved. Chapter 6 describes the approach to tailor the energy levels of conjugated polymers (PTDPP-IDT and PTTDPP-IDT) based on Indacenodithiophene (IDT) coupled with DPP moieties. We have studied the photovoltaic performance of these conjugated polymers by blending with PCBM and P3HT. The importance of these materials in polymer/polymer blend solar cell has been emphasized. The photovoltaic devices with polymer/polymer blend solar cell exhibit high open-circuit voltages (VOC) of ~ 0.8 V. In summary, the work presented in this thesis describes synthesis, characterization and photophysical properties of new organic semiconductors and their importance in optoelectronic devices. This work also describes a general design principle of nonfullerene organic solar cell. The results described here show that these materials have potential application as active components in plastic electronics.

In this thesis we research distributed pair programming by making an explorative study of a distributed pair programming method, screen-viewing distributed pair programming. This method has a user share the visual contents of his screen with other users in order to enable collaboration. This study is conducted by distributing a questionnaire to undergraduate students and analyzing the results. The students were required to have previous experience with screen-viewing distributed programming. This is a practice where two pieces of software are utilized, one for sharing the computer display with the programming partner and another for sharing the code written together. Our goal is to contribute to the knowledge of pair programming and how it can be applied in these kinds of environments while giving further insight into benefits and drawbacks about the usage of the screen-viewing distributed pair programming. This thesis is of an explorative nature. Surveys from students constitute the bulk of the data set which was analysed using pie charts and tables. The survey questions were based on a previous article about distributed pair programming utilizing a synchronized development environment, written by Stelios Xinogalos, Maya Satratzemi, Alexander Chatzigeorgiou and Despina Tsom-panoudi. The results of the study indicated that the screen-viewing distributed pair programming approach experienced many benefits but also some drawbacks. These results are similar to what distributed pair programming with a synchronized development environment experiences. The students also experience a high satisfaction in partner choice regardless of being free to select their own partner or if they are allocated one. A majority of the respondents would prefer to work collaboratively in the future with regards to their screen-viewing distributed pair programming experience. Because the perceived benefits incurred from the screen-viewing distributed pair programming is similar to the benefits of a synchronized development environment, we conclude that the perceived benefits are not necessarily bound to the choice of method. Screen-viewing distributed pair programming is split into two main aspects, screen-viewing and code sharing. The screen-viewing part represented a smaller amount of perceived issues while the code sharing part represented a larger part. We conclude that there are difficulties with this approach, however that a substantial part are confined to the code-sharing aspect. / I denna studie granskar vi distribuerad parprogrammering genom att utföra en utforskande studie på en distribuerad parprogrammerings-metod, skärmdelnings-distribuerad parprogrammering. Metoden har en användare som delar sitt visuella innehåll på sin skärm med andra användare för att möjligöra samarbete. Denna studie utförs genom att ett frågeformulär delades ut till studenter på kandidatnivå, vars resultat analyserades. Studenterna som tillfrågades hade tidigare erfarenhet av distribuerad parprogrammering med hjälp av skärmdelning, en metod som består av mjukvara för delning av skärm och en för att dela den kod som skrivits tillsammans. Målet med denna studie är att bidra med ökad insikt i parprogrammering och kunskap om hur ramverket kan appliceras i dessa omgivningar, samtidigt som vi ger vidare kännedom angående fördelar och nackdelar vid användning av skärmdelnings-distribuerad parprogrammering. Studien är utforskande. Svar från framtaget frågeformulär utgör studiens datauppsättning som utvärderas med hjälp av cirkeldiagram och tabeller. Frågeformulärets frågor är baserade på en tidigare artikel om distribuerad parprogrammering där en synkroniserad arbetsmiljö användes, skrivet av Stelios Xinogalos, Maya Satratzemi, Alexander Chatzigeorgiou and Despina Tsom- panoudi. Studiens resultat pekar på att många fördelar upplevdes med skärmdelnings-distribuerad parprogrammering men även ett antal nackdelar. Dessa reultat liknar de som tagits fram i tidigare studier om distribuerad parprogrammering med hjälp av en synkroniserad miljö. Inblandade studenter upplever stor tillfredsställelse med sina samarbetspartners oavsett om studenterna hade möjligheten att välja partner själv eller var tilldelade partner. En majoritet av respondenterna föredrar att arbeta i grupp i framtiden, baserat på deras upplevelser med skärmdelnings-distribuerad parprogrammering. Då de uppfattade fördelarna med skärmdelnings-distribuerad parprogrammering liknar de som resulterat från parprogrammering med hjälp av en synkronierad arbetsmiljö i tidigare studier, så drar vi slutsatsen att fördelarna inte är bundna till något specifikt val av metodik. Skärmdelnings-distribuerad parprogrammering delas upp i två komponenter, skärmdelning och koddelning. Skärmdelningen bidrar med en mindre mängd upplevda nackdelar, och koddelning bidrar med en större del av de upplevda nackdelarna. Vi drar slutsatsen att nackdelar fortfarande är närvarande. Däremot dras slutsatsen att dessa nackdelar är mer begränsade till koddelningens komponent mer än skärmdelningen och att det därför finns utrymme för vidare fokuserad förbättring.

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This thesis provides insights into the feasibility of managing product requirements in a concept leveraging an object-centric information model. The aim of this concept is to provide efective management of product requirements in the context of rising volume and complexity of requirements. Firstly, benefts and challenges between the current document-centric way of managing requirements and the novel object-centric concept for managing requirements are mapped and presented. Secondly, the organizational prerequisites necessary for adopting the object-centric product requirement applicability concept are explored and insights into how this transition can be facilitated with knowledge management are generated. Thirdly, the accuracy of this novel concept is evaluated in terms of applying the correct requirements onto products and not more nor less. The methods in this thesis are of mixed nature and combine qualitative and quantitative data sets. The quantitative data was collected from the analysis of the requirement applicability concept and the previous tests of the same concept on diferent products at Company X. The analysis of quantitative data for concept accuracy revolved around interpreting the nature of negative- and positive delta values following an automatic application of requirements in the novel object-centric concept. The former of these delta values relates to relevant requirements missing onto products whereas the latter relates to non-relevant requirements being applied following the automatic application. The qualitative data was collected mainly through a comprehensive literature review, semi-structured interviews, a workshop, meetings, Company X documents and observations. The analysis of qualitative data was done via an adaptation of two frameworks: The Multi-Dimensional Framework for Digital Transformation by Hanelt et al, 2021 and The Process of Organizational Knowledge Creation by Nonaka, 1994. These adapted frameworks were leveraged to generate insights into the necessary organizational prerequisites for adopting the object-centric product requirement applicability concept. While benefts and challenges exist between the two diferent ways of managing requirements, these are not weighted and thus no defnitive conclusion on best practice is drawn. Instead these fndings provide organizations a reference point for evaluating each approach in relation to their own circumstances. Some of the prerequisites identifed as critical for adopting an object-centric product requirement applicability model are a digital library of requirement specifcations that are convertible to object-centric data format, and a suitable PLM strategy chosen by the Top Management Teams that is aiding the development of the concept. As for knowledge management in order to transition to the new concept, fndings show that standardized knowledge creation and knowledge exchange is necessary as well as developing centralized knowledge databases. Lastly, the quantitative fndings indicate that the applicability concept is accurate, but that there is a need for additional iterations with model improvements where the negative delta can be eliminated and the positive delta held at an acceptable level. / Den här studien ger insikter om genomförbarheten av att hantera produktkrav i ett koncept som utnyttjar en objektcentrerad informationsmodell. Syftet med detta koncept är att tillhandahålla efektiv hantering av produktkrav i samband med att de ökar i volym samt komplexitet. Studien kartlägger först fördelar och utmaningar mellan det nuvarande dokumentcentrerade sättet att hantera krav och det nya objektcentrerade konceptet. Även de organisatoriska förutsättningar som krävs för att införa det objektcentrerade produktkravskonceptet undersöks i samband med hur denna övergång kan underlättas med hjälp av kunskapshantering. Slutligen så utvärderas det objektcentrerade konceptet för kravapplicering beträfande hur exakt konceptet är i att applicera rätt krav på produkter. Metodiken i denna studie kombinerar kvalitativa och kvantitativa datamängder. Den kvantitativa datan samlades in från analys av kravappliceringskonceptet samt de tidigare testerna av konceptet på olika produkter som gjorts av Företag X. Analysen av kvantitativ data för hur exakt konceptet är i att applicera rätt krav kretsar kring att förstå grundorsakerna till de negativa och positiva deltavärden som uppkommit efter en automatisk applicering av krav i det nya objektcentrerade konceptet. Det negativa deltavärdet relaterar till nödvändiga krav som saknas på produkter, medan det positiva deltavärdet avser icke-relevanta krav som har applicerats efter en systemförfrågan och automatisk applicering av krav. Den kvalitativa datan samlades huvudsakligen in genom en omfattande litteraturstudie, semistrukturerade intervjuer, workshops, möten, dokument från Företag X och observationer. Analysen av kvalitativ data gjordes via en anpassning av två vetenskapliga ramverk: The Multi-Dimensional Framework for Digital Transformation av Hanelt et al, 2021 och The Process of Organizational Knowledge Creation av Nonaka, 1994. Dessa anpassade ramverk utnyttjas för att generera insikter i de nödvändiga organisatoriska förutsättningarna som krävs för att införa det objektcentrerade kravappliceringskonceptet i en organisation. Fördelar och utmaningar med de två olika sätten att hantera krav viktades inte i denna studie, därför dras ingen defnitiv slutsats om bästa praxis. Istället ger dessa fynd en referenspunkt till organisationer att utvärdera bästa praxis i förhållande till sina egna omständigheter. Några av förutsättningarna identiferade som kritiska för att tillämpa en objektcentrerad produktkravappliceringsmodell är ett digitalt bibliotek av kravspecifkationer som är konverterbara till objektcentrerat dataformat, samt en PLM-strategi införd av de högsta ledningsgrupperna som hjälper till med stödja det objekcentrerade konceptet för produktkravsapplicering. Vad gäller kunskapshantering för att övergå till det nya konceptet visar resultaten att standardiserad kunskapsskapande och utbyte av kunskap är nödvändigt, samt utvecklingen av centraliserade kunskapsdatabaser. Slutligen indikerar de kvantitativa resultaten att tillämpningskonceptet är noggrant, men att ytterligare iterationer med modellförbättringar behövs där den negativa deltan kan elimineras och där den positiva deltan hålls på en acceptabel nivå.

By the end of the twentieth century, there were many secessionist groups, but, the move towards Taiwanese secessionism has arguably been the most significant of these. It triggered the 1996 Taiwan Strait Crisis, which resulted in a historical military confrontation between Mainland China and the US. As will be shown, from 1988 to 2000, Lee Teng-hui, as president of Taiwan, manipulated the political Cross-Straits relationship to promote what was ultimately a secessionist policy. This caused Mainland China to react strongly and triggered sharp tension between Taiwan and Mainland China. This thesis considers what motivated Lee Teng-hui to implement a secessionist Cross-Straits policy and why he supported unification while adopting a substantive secessionist policy. It looks at how he was able to instigate Taiwanese hostility towards Mainlanders, to transform the hostility into a sense of Taiwanese national identity and ultimately into Taiwanese secessionist ideology. A historical approach was used in exploring the origins of secessionism, and descriptive and analytical methods to review systematically and comprehensively political developments in the ROC and its civil war, and to study Lee Teng-hui’s life; the national identity of Taiwan and Mainland China; the implementation of Lee Teng-hui’s political Cross-Straits policy; and the reaction of Mainland China. The study showed that the main cause of Taiwanese secessionism was ethnic conflict between Taiwanese and Mainlanders. It originated from the 228 Incident of 1947, in which Mainlander-led troops slaughtered many Taiwanese. Soon after, the Mainlander-led government fled to Taiwan from Mainland China, and many Taiwanese (including Mainlanders) were killed during the State of Emergency in the 1950s and 1960s. Since the Mainlander-led government fled to Taiwan in its original central government form, the Mainlander élite occupied key positions in the government during the 1950s and 1960s. It resulted in unfair power-sharing for Taiwanese, and caused the Taiwanese élite to believe that they had to establish their own government (nation). Lee Teng-hui had participated in the CCP and had been under political surveillance by the Mainlander-led government for over twenty years. He weathered these political difficulties, but by reasonable inference, there was a close relationship between the political oppression by the Mainlander-led government and his secessionist political Cross-Straits policy. Because Taiwanese residents were indoctrinated by Chiang Ching-kuo and his father, Chiang Kai-shek’s administration for about 40 years, Chinese ideology was dominant and Lee Teng-hui initially paid lip-service to Cross-Strait unification whilst working towards secessionism as reflected in the Chingdao-Lake Incident (1994); the private dialogue between Lee Teng-hui and Shiba Ryotaro (1994); the address at Cornell University (1995); and his two-state theory (1999). However, due to strong pressure from Mainland China, he did not reach his secessionist goal during his presidential term (1988-2000). In conclusion, this thesis shows that Taiwan Island’s geopolitical importance is at the heart of the US’ support for Taiwan’s secession from the Mainland. Therefore, Lee’s secessionist Cross-Strait policy aside, US national interests lie in containing Mainland China and it has, therefore, always played an important role in the secessionist issue and always will. From the perspective of Mainland China, either in terms of nationalism or national security, Taiwan’s secession is a life-and-death issue. If Taiwanese authorities were to declare independence, the only option for Mainland China would be to launch a unification war. For the US, Taiwan is only a pawn that it uses to contain Mainland China. Therefore, in the Cross-Strait issue, the US has more options than Mainland China, namely, to use military intervention in the future to deter Chinese unification or to decide to share common peaceful international relations with Mainland China by accepting Cross-Strait unification. / Thesis (DPhil (International Relations))--University of Pretoria, 2004. / Political Sciences / unrestricted