Optical Characterization of the Hole Polaron in a Series of Diketopyrrolopyrrole Polymers Used for Organic Photovoltaics

Abstract: A strategy that is often used for designing low band gap polymers involves the incorporation of electron-rich (donor) and electron-deficient (acceptor) conjugated segments within the polymer backbone. In this paper we investigate such a series of Diketopyrrolopyrrole (DPP)-based co-polymers. The co-polymers consisted of a DPP unit attached to a phenylene, naphthalene, or anthracene unit. Additionally, polymers utilizing either the thiophene-flanked DPP or the furan-flanked DPP units paired with the naphthalene comonomer were compared. As these polymers have been used as donor materials and subsequent hole transporting materials in organic solar cells, we are specifically interested in characterizing the optical absorption of the hole polaron of these DPP based copolymers. We employ chemical doping, electrochemical doping, and photoinduced absorption (PIA) studies to probe the hole polaron absorption spectra. While some donor-acceptor polymers have shown an appreciable capacity to generate free charge carriers upon photoexcitation, no polaron signal was observed in the PIA spectrum of the polymers in this study. The relations between molecular structure and optical properties are discussed. Keywords: organic solar cell; organic photovoltaic; diketopyrrolopyrrole; chemical doping; spectroelectrochemistry; photoinduced absorption; hole polaron

Time-independent charge carrier mobility in a model polymer:fullerene organic solar cell

The technique of photo-CELIV (charge extraction by linearly increasing voltage) is one of the more straightforward and popular approaches to measure the faster carrier mobility in measurement geometries that are relevant for operational solar cells and other optoelectronic devices. It has been used to demonstrate a time-dependent photocarrier mobility in pristine polymers, attributed to energetic relaxation within the density of states. Conversely, in solar cell blends, the presence or absence of such energetic relaxation on transport timescales remains under debate. We developed a complete numerical model and performed photo-CELIV experiments on the model high efficiency organic solar cell blend poly[3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-naphthalene] (PDPP-TNT):[6,6]-phenyl-C71-butyric-acid-methyl-ester (PC70BM). In the studied solar cells a constant, time-independent mobility on the scale relevant to charge extraction was observed, where thermalisation of photocarriers occurs on time scales much shorter than the transit time. Therefore, photocarrier relaxation effects are insignificant for charge transport in these efficient photovoltaic devices.

Thiophene–tetrafluorophenyl–thiophene : a promising building block for ambipolar organic field effect transistors

A thiophene–tetrafluorophenyl–thiophene donor–acceptor–donor building block was used in combination with a furan-substituted diketopyrrolopyrrole for synthesizing the polymer semiconductor, PDPPF-TFPT. Due to the balance of tetrafluorophenylene/diketopyrrolopyrrole electron-withdrawing and furan/thiophene electron-donating moieties in the backbone, PDPPF-TFPT exhibits ambipolar behaviour in organic thin-film transistors, with hole and electron mobilities as high as 0.40 cm2 V−1 s−1 and 0.12 cm2 V−1 s−1.

Changing influences on the concept of ‘media influence’

The concept of media influence has a long history in media and communication studies, and has also had significant influence on public policy. This article revisits questions of media influence through three short case studies. First, it critically analyses the strongly partisan position of News Corporation’s newspapers against the Labor government during the 2013 Australian Federal election to consider whether the potential for media influence equated to the effective use of media power. Second, it discusses the assumption in broadcasting legislation, in both the United Kingdom and Australia, that terrestrial broadcasting should be subject to more content regulation than subscription services, and notes the new challenges arising from digital television and over-the-top video streaming services. Finally, it discusses the rise of multi-platform global content aggregators such as Google, Apple, Microsoft and others, and how their rise necessitates changes in ways of thinking about concentration of media ownership, and regulations that may ensue from it.

Identification of the sources of primary organic aerosols at urban schools : a molecular marker approach

Children are particularly susceptible to air pollution and schools are examples of urban microenvironments that can account for a large portion of children’s exposure to airborne particles. Thus this paper aimed to determine the sources of primary airborne particles that children are exposed to at school by analyzing selected organic molecular markers at 11 urban schools in Brisbane, Australia. Positive matrix factorization analysis identified four sources at the schools: vehicle emissions, biomass burning, meat cooking and plant wax emissions accounting for 45%, 29%, 16% and 7%, of the organic carbon respectively. Biomass burning peaked in winter due to prescribed burning of bushland around Brisbane. Overall, the results indicated that both local (traffic) and regional (biomass burning) sources of primary organic aerosols influence the levels of ambient particles that children are exposed at the schools. These results have implications for potential control strategies for mitigating exposure at schools.

Trial by media: An empirical investigation of corporate reputation and stock returns in Australia

This article examines whether investors are able to generate abnormal risk-adjusted returns in the Australian market based on media-specific firm reputational factors under market uncertainty between 2004 and 2012. The findings suggest that after controlling for crisis-centric time periods and market risk factors, contrarian trading strategies produce abnormal returns for poor corporate reputation firms but not for their good corporate reputation counterparts. Corporate reputation may be a driver of performance for poorly performing Australian firms and could be considered a stimulus for trading activity due to its explanatory capabilities.

Social media(tion) and the reshaping of public/private boundaries in employment relations

Tensions surrounding social media in the employment relationship are increasingly evident in the media, public rhetoric, and courts and employment tribunals. Yet the underlying causes and dimensions of these tensions have remained largely unexplored. This article firstly reviews the available literature addressing social media and employment, outlining three primary sources of contestation: profiling, disparaging posts and blogs, and private use of social media during work time. In each area, the key dynamics and underlying concerns of the central actors involved are identified. The article then seeks to canvas explanations for these forms of contestation associated with social media at work. It is argued that the architecture of social media disrupts traditional relations in organisational life by driving employer and employee actions that (re)shape and (re)constitute the boundaries between public and private spheres. Although employers and employees are using the same social technologies, their respective concerns about and points of entry to these technologies, in contrast to traditional manifestations of conflict and resistance, are asymmetric. The article concludes with a representational summary of the relative legitimacy of concerns for organisational actors and outlines areas for future research.

Citizens and social media in times of natural disaster: Exploring information experience

Introduction. Social media is becoming a vital source of information in disaster or emergency situations. While a growing number of studies have explored the use of social media in natural disasters by emergency staff, military personnel, medial and other professionals, very few studies have investigated the use of social media by members of the public. The purpose of this paper is to explore citizens’ information experiences in social media during times of natural disaster. Method. A qualitative research approach was applied. Data was collected via in-depth interviews. Twenty-five people who used social media during a natural disaster in Australia participated in the study. Analysis. Audio recordings of interviews and interview transcripts provided the empirical material for data analysis. Data was analysed using structural and focussed coding methods. Results. Eight key themes depicting various aspects of participants’ information experience during a natural disaster were uncovered by the study: connected; wellbeing; coping; help; brokerage; journalism; supplementary and characteristics. Conclusion. This study contributes insights into social media’s potential for developing community disaster resilience and promotes discussion about the value of civic participation in social media when such circumstances occur. These findings also contribute to our understanding of information experiences as a new informational research object.

Numerical simulation of anomalous infiltration in porous media

Nonlinear time-fractional diffusion equations have been used to describe the liquid infiltration for both subdiffusion and superdiffusion in porous media. In this paper, some problems of anomalous infiltration with a variable-order timefractional derivative in porous media are considered. The time-fractional Boussinesq equation is also considered. Two computationally efficient implicit numerical schemes for the diffusion and wave-diffusion equations are proposed. Numerical examples are provided to show that the numerical methods are computationally efficient.

Changing the game: The role of social media in overcoming old media's attention deficit toward women's sport

Social media is now an integral part of modern sports broadcasting, which combines old and new media into a redefined and multidimensional experience for fans. The popularity of social media has particular implications for professional women's sports due to this convergence, and may be utilised by organisations to address some of the issues women's sports face from a lack of traditional broadcast coverage. This article discusses Twitter activity surrounding the ANZ Championship netball competition and analyses the ways social media can help transcend the structural challenges that “old” media has placed on professional women's sports.

Working on the edge : Exploring the creative tensions experienced by practitioners facilitating participatory media projects with refugees and asylum seekers in Australia

This paper aims to provide a contextualised and embedded exploration of how the notions of "practice" and "participation", key concepts in the study of culture and media, are manifest in an example of a complex creative project. This project aimed to engage with refugees and asylum seekers through the co-creation of cultural material and is an outcome of an? ethnographic action research (Tacchi et al. 2003) partnership involving a community development worker in a settlement support agency and a storytelling/community media researcher (the author), along with other project collaborators. The discussion of this project focuses on the role of the facilitator and illustrates the processes of orchestrating a complex project involving a series of linked stages with cumulative effect. As practitioners at this site we are working in the space where personal narratives, participatory arts and media, and the staging of intercultural, civic dialogue events, intersect. Co-creative media facilitation in these contexts involves both managing hybrid communicative spaces and (re)combining the "integrative practices" (Schatzki 1996) of a range of professional approaches and creative roles. This is liminal work, located on the boundaries of several disciplines and practices. Drawing on reflections gathered from collaborative ethnographic descriptions (Bhattacharya 2008), this paper traces moments of practitioner uncertainty that can be linked to the way "practice" and “participation” is problematised within the community cultural development field in a way that is at times an uneasy fit with conventional ways of operating in social service roles. These moments of tension also indicate where this project pushed practitioners into spaces of improvisation and new learning. Keywords: Youth, refugees, community cultural development, co-creative media facilitation, ethnographic action research, intercultural dialogue.

Australian print media framing of mandatory reporting

Mandatory reporting is a key aspect of Australia’s approach to protecting children and is incorporated into all jurisdictions’ legislation, albeit in a variety of forms. In this article we examine all major newspaper’s coverage of mandatory reporting during an 18-month period in 2008-2009, when high-profile tragedies and inquiries occurred and significant policy and reform agendas were being debated. Mass media utilise a variety of lenses to inform and shape public responses and attitudes to reported events. We use frame analysis to identify the ways in which stories were composed and presented, and how language portrayed this contested area of policy. The results indicate that within an overall portrayal of system failure and the need for reform, the coverage placed major responsibility on child protection agencies for the over-reporting, under-reporting, and overburdened system identified, along with the failure of mandatory reporting to reduce risk. The implications for ongoing reform are explored along with the need for robust research to inform debate about the merits of mandatory reporting.

Life storytelling at the ABC: Challenges of 'giving the audience a voice' in the context of public service media

Life storytelling projects have become an important means through which public service media institutions such as the Australian Broadcasting Corporation are seeking to foster audience participation and involve particular cohorts in the creation and distribution of broadcast content. This paper contributes to the wider conversation on audience participation within public service media intuitions (PSMs), and focuses on the opportunities and challenges that arise within life storytelling projects that are facilitated by these institutions, and that aim to ‘give voice’ to members of ‘the audience’. In particular, it focuses on two of the Australian Broadcasting Corporation’s current life storytelling projects: ABC Open and Heywire.

Co-creating stories in social learning systems : The role of community media and cultural organisations in disseminating knowledge

This paper investigates how community based media organisations are co-creative storytelling institutions, and how they learn to disseminate knowledge in a social learning system. Organisations involved in story co-creation are learning to create in fluid environments.They are project based, with a constant turnover of volunteers or staff. These organisations have to meet the needs of their funding bodies and their communities to remain sustainable. Learning is seen as dialogical, and this is also reflected in the nature of storytelling itself. These organisations must learn to meet the needs of their communities, who in turn learn from the organisation’s expertise in a facilitated setting. This learning is participatory and collaborative, and is often a mix of virtual and offline interaction. Such community-based organisations sit in the realm of a hybrid-learning environment; they are neither a formal educational institution like a college, nor do their volunteers produce outcomes in a professional capacity. Yet, they must maintain a certain level of quality outcomes from their contributors to be of continued value in their communities. Drawing from a larger research study, one particular example is that of the CitizenJ project. CitizenJ is hosted by a state cultural centre, and partnered with publishing partners in the community broadcasting sector. This paper explores how this project is a Community of Practice, and how it promotes ethical and best practice, meets contributors’ needs, emphasises the importance of facilitation in achieving quality outcomes, and the creation of projects for wider community and public interest.

The Media as Political Actors

This chapter provides a history of the media as political actors and identifies key principles that have shaped their role in both democratic and authoritarian polities (i.e., information, interpretation, participation, critical scrutiny). In addition, the chapter explores recent trends impacting on the performance of that role, such as the emergence of the Internet and, as a consequence of that process, a globalized public sphere of transnational news media outlets. It is argued that to make the Internet truly valuable as a political resource, democratic societies continue to require the work of skilled, professional journalists and their sense making, interpretative functions. Because of that journalists and their organizations remain crucial to the translation of content into meaningful messages.