High mobility top-gate and dual-gate polymer thin-film transistors based on diketopyrrolopyrrole-naphthalene copolymer

In this letter, the performance characteristics of top-gate and dual-gate thin-film transistors (TFTs) with active semiconductor layers consisting of diketopyrrolopyrrole-naphthalene copolymer are described. Optimized top-gate TFTs possess mobilities of up to 1 cm 2 /V s with low contact resistance and reduced hysteresis in air. Dual-gate devices possess higher drive currents as well as improved subthreshold and above threshold characteristics compared to single-gate devices. We also describe the reasons that dual-gate devices result in improved performance. The good stability of this polymer combined with their promising electrical properties make this material a very promising semiconductor for printable electronics.

Characteristics of high-performance ambipolar organic field-effect transistors based on a diketopyrrolopyrrole-benzothiadiazole copolymer

In this paper, we report the device characteristics of ambipolar thin-film transistors (TFTs) based on a diketopyrrolopyrrole-benzothiadiazole copolymer. This polymer semiconductor exhibits the largest comparable electron and hole mobility values in a single organic semiconductor. The key to realizing such high mobility values, which are $0.5&cm}{2}/\hbox{V}̇\hbox{s, is molecular design, i.e., the use of suitable surface treatments of the source/drain contact electrodes and device architectures, particularly top-gate configurations. The subthreshold characteristics of the TFT devices are greatly improved by the use of dual-gate device geometry. We also report the first measurement of the velocity distribution of electron and hole velocities in an ambipolar organic semiconductor.

3,6-Di(furan-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione and bithiophene copolymer with rather disordered chain orientation showing high mobility in organic thin film transistors

Pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione or diketopyrrolopyrrole (DPP) is a useful electron-withdrawing fused aromatic moiety for the preparation of donor-acceptor polymers as active semiconductors for organic electronics. This study uses a DPP-furan-containing building block, 3,6-di(furan-2-yl)pyrrolo[3,4- c]pyrrole-1,4(2H,5H)-dione (DBF), to couple with a 2,2′-bithiophene unit, forming a new donor-acceptor copolymer, PDBFBT. Compared to its structural analogue, 3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DBT), DBF is found to cause blue shifts of the absorption spectra both in solution and in thin films and a slight reduction of the highest occupied molecular orbital (HOMO) energy level of the resulting PDBFBT. Despite the fact that its thin films are less crystalline and have a rather disordered chain orientation in the crystalline domains, PDBFBT shows very high hole mobility up to 1.54 cm 2 V-1 s-1 in bottom-gate, top-contact organic thin film transistors.

A furan-containing conjugated polymer for high mobility ambipolar organic thin film transistors

Furan substituted diketopyrrolopyrrole (DBF) combined with benzothiadiazole based polymer semiconductor PDPP-FBF has been synthesized and evaluated as an ambipolar semiconductor in organic thin-film transistors. Hole and electron mobilities as high as 0.20 cm 2 V -1 s -1 and 0.56 cm 2 V -1 s -1, respectively, are achieved for PDPP-FBF.

A fluorenone based low band gap solution processable copolymer for air stable and high mobility organic field effect transistors

A fluorenone based alternating copolymer (PFN-DPPF) with a furan based fused aromatic moiety has been designed and synthesized. PFN-DPPF exhibits a small band gap with a lower HOMO value. Testing this polymer semiconductor as the active layer in organic thin-film transistors results in hole mobilities as high as 0.15 cm2 V-1 s-1 in air.

High-mobility organic thin film transistors based on benzothiadiazole- sandwiched dihexylquaterthiophenes

We report here the synthesis, characterization, and organic thin-film transistor (OTFT) mobilities of 4,7-bis(5-(5-hexylthiophen-2-yl)thiophen-2-yl) benzo[1,2,5]thiadiazole (DH-BTZ-4T). DH-BTZ-4T was prepared in one high-yield step from commercially available materials using Suzuki chemistry and purified by column chromatography. OTFTs with hole mobilities of 0.17 cm2/(Vs) and on/off current ratios of 1 × 105 were prepared from DH-BTZ-4T active layers deposited by vacuum deposition. As DH-BTZ-4T is soluble in common solvents, solution processed devices were also prepared by spin coating yielding preliminary mobilities of 6.0 × 10-3 cm 2/(Vs). The promising mobilities and low band gap (1.90 eV) coupled with solution processability and ambient stability makes this material an excellent candidate for application in organic electronics.

Isoindigo dye incorporated copolymers with naphthalene and anthracene: promising materials for stable organic field effect transistors

In this paper, we report the design and synthesis of isoindigo based low band gap polymer semiconductors, poly{N,N′-(2-octyldodecyl)-isoindigo-alt- naphthalene} (PISD-NAP) and poly{N,N′-(2-octyldodecyl)-isoindigo-alt- anthracene} (PISD-ANT). A series of donor-acceptor (D-A) copolymers can be prepared where donor and acceptor conjugated blocks can be attached alternately using organometallic coupling. In these polymers, an isoindigo dye acceptor moiety has been attached alternately with naphthalene and anthracene donor comonomer blocks by Suzuki coupling. PISD-NAP and PISD-ANT exhibit excellent solution processibility and good film-forming properties. Gel permeation chromatography exhibits a higher molecular mass with lower polydispersity. UV-vis-NIR absorption of these polymers exhibits a wide absorption band ranging from 300 nm to 800 nm, indicating the low band gap nature of the polymers. Optical band gaps calculated from the solid state absorption cutoff value for PISD-NAP and PISD-ANT are around 1.80 eV and 1.75 eV, respectively. Highest occupied molecular orbital (HOMO) values calculated respectively for PISD-NAP and PISD-ANT thin films on glass substrate by photoelectron spectroscopy in air (PESA) are 5.66 eV and 5.53 eV, indicative of the good stability of these materials in organic electronic device applications. These polymers exhibit p-channel charge transport characteristics when used as the active semiconductor in organic thin-film transistor (OTFT) devices in ambient conditions. The highest hole mobility of 0.013 cm2 V-1 s-1 is achieved in top contact and bottom-gate OTFT devices for PISD-ANT, whereas polymer PISD-NAP exhibited a hole mobility of 0.004 cm2 V -1 s-1. When these polymer semiconductors were used as a donor and PC71BM as an acceptor in OPV devices, the highest power conversion efficiency (PCE) of 1.13% is obtained for the PISD-ANT polymer.

Nonvolatile multilevel data storage memory device from controlled ambipolar charge trapping mechanism

The capability of storing multi-bit information is one of the most important challenges in memory technologies. An ambipolar polymer which intrinsically has the ability to transport electrons and holes as a semiconducting layer provides an opportunity for the charge trapping layer to trap both electrons and holes efficiently. Here, we achieved large memory window and distinct multilevel data storage by utilizing the phenomena of ambipolar charge trapping mechanism. As fabricated flexible memory devices display five well-defined data levels with good endurance and retention properties showing potential application in printed electronics.

Mobility in the child (and carer) friendly city : SEQ vs. Stockholm

The rationale for providing state subsidised public transport has changed over time from a social obligation to provide transport options for those without access to private transport to an environmental and economic imperative to minimize congestion and greenhouse gas emissions. In many jurisdictions this shift has seen a greater focus on the provision of peak hour commuter services and a shift in the demographic profile of the riding public and a significant increase in the number of commuter passengers relative to others. The scheduling of commuter services is not geared to meet the needs of children and their generally female carers who often need to engage in trip chaining and travel outside peak commuting periods and on weekends. In addition to service scheduling difficulties, transport infrastructure, both on-board and supporting infrastructure such as bus stops, train stations and connecting footpaths often do not support children and their carers to use public transport services. Combined with a negative attitude by passengers and service providers, such as bus drivers, which may see children, babies and young people as out of place and unwelcome on commuter services, these issues conspire to hinder the use of public transport by children and their carers. Overlaying feminist geography analysis and insights and child-friendly cities objectives, this paper proposes some basic criteria for the provision of public transport services and supporting infrastructure which meets the needs of children, babies and their carers and juxtaposes the achievement of these in South East Queensland, Australia and Stockholm, Sweden.

The Journey of Becoming Involved in Urban Spaces by Children with Diverse Mobility

Participation is a word frequently espoused in the literature of childhood and urban studies. It has also been made sacrosanct through the Convention on the Rights of the Child and other rights-based policy and programming. Despite this importance, what it means and how it is experienced in the everyday lives of children with diverse abilities is not well understood. This chapter provides insight into the everyday experiences of participation by ten children 9-12 years of age, who have diverse personal mobility from various physical conditions that affect muscle and movement differently, including: Muscular Dystrophy, Cerebral Palsy, and Autoimmune Rheumatic Diseases. The children participants live in the outer suburbs and inner regions of south-east Queensland, Australia. The chapter discusses a new way of understanding and theorising participation as a journey of becoming involved. This knowledge emerged through the children’s body-space-time routines (body ballets) and their descriptions of inhabiting urban space. This chapter also establishes how body-space-context interplays shape the experiences of becoming and being involved in everyday life, as well as the preconceptions of body embed in space which divide and constrain children and families actualisation of full and genuine participation.

Learned stochastic mobility prediction for planning with control uncertainty on unstructured terrain

Motion planning for planetary rovers must consider control uncertainty in order to maintain the safety of the platform during navigation. Modelling such control uncertainty is difficult due to the complex interaction between the platform and its environment. In this paper, we propose a motion planning approach whereby the outcome of control actions is learned from experience and represented statistically using a Gaussian process regression model. This mobility prediction model is trained using sample executions of motion primitives on representative terrain, and predicts the future outcome of control actions on similar terrain. Using Gaussian process regression allows us to exploit its inherent measure of prediction uncertainty in planning. We integrate mobility prediction into a Markov decision process framework and use dynamic programming to construct a control policy for navigation to a goal region in a terrain map built using an on-board depth sensor. We consider both rigid terrain, consisting of uneven ground, small rocks, and non-traversable rocks, and also deformable terrain. We introduce two methods for training the mobility prediction model from either proprioceptive or exteroceptive observations, and report results from nearly 300 experimental trials using a planetary rover platform in a Mars-analogue environment. Our results validate the approach and demonstrate the value of planning under uncertainty for safe and reliable navigation.

A/Effective connections : mobility, technology and well-being

This article investigates the significance of internet communication technologies for mediating affect in ways that help promote feelings of well-being among recently arrived migrants from culturally and linguistically diverse communities (CALD) in Australia. It is based on a qualitative study that focuses on the internet's communicative capabilities for maintaining kinship ties in homeland countries, and for forging new connections in the host city of Brisbane during the early re-settlement period. Through the experience of ‘presence’ and affective communities, it emphasizes the ways in which visually mediated interaction helps to combat feelings of social isolation and loneliness. The study finds that internet use is creating new forms of sociality among migrants and plays a key role in the re-settlement period. It highlights the importance of publicly available computers and training for migrants.

Migrants, refugees and mobility : how useful are information communication technologies in the first phase of resettlement?

The rate at which people move and resettle around the world is unprecedented. Mobility and resettlement is now greatly assisted by the use of inexpensive internet communication technologies (ICTs) for a wide variety of functions: to communicate locally and across territories, for localised information seeking, geo – locational mapping and for forging new social connections in host countries and cities. This article is based on a qualitative study of newly arrived migrants and mobile people from non English speaking backgrounds (NESB) to the city of Brisbane, Australia and investigates how the internet is used to assist the initial period of settling into the city. As increasing amounts of essential information is placed online, the study asks how people from NESB communities manage to negotiate the types of information they require during the early stages of resettlement, given varying levels of access to ICTs, digital and language literacy. The study finds that the internet is widely used for specific location information seeking (such as accommodation and job-seeking), but this is often supplemented with other non-mediated sources of information. The study identified implications for social policy in regard to the resourcing and access of information. While findings are specific to the study location, it is feasible that the patterns of internet use for resettlement have relevance in a broader context.

Understanding public response to a congestion charge : a random-effects ordered logit approach

Public acceptance is consistently listed as having an enormous impact on the implementation and success of a congestion charge scheme. This paper investigates public acceptance of such a scheme in Australia. Surveys were conducted in Brisbane and Melbourne, the two fastest growing Australian cities. Using an ordered logit modeling approach, the survey data including stated preferences were analyzed to pinpoint the important factors influencing people’s attitudes to a congestion charge and, in turn, to their transport mode choices. To accommodate the nature of, and to account for the resulting heterogeneity of the panel data, random effects were considered in the models. As expected, this study found that the amount of the congestion charge and the financial benefits of implementing it have a significant influence on respondents’ support for the charge and on the likelihood of their taking a bus to city areas. However, respondents’ current primary transport mode for travelling to the city areas has a more pronounced impact. Meanwhile, respondents’ perceptions of the congestion charge’s role in protecting the environment by reducing vehicle emissions, and of the extent to which the charge would mean that they travelled less frequently to the city for shopping or entertainment, also have a significant impact on their level of support for its implementation. We also found and explained notable differences across two cities. Finally, findings from this study have been fully discussed in relation to the literature.