. π-Conjugated molecules with fused rings for organic field-effect transistors: design, synthesis and applications. Chemical Society Reviews, 39(5), pp. 1489-1502. doi: 10.1039/b813123f This is the accepted version of the paper.This version of the publication may differ from the final published version. π-Conjugated molecular materials with fused rings are the focus of considerable interest in the emerging area of organic electronics, since the combination of excellent charge carrier mobility and high stability may lead to their practical applications. This tutorial review discusses the synthesis, properties and applications of π-conjugated organic semiconducting materials especially those with fused rings. The achievements to date, the remaining problems and challenges, and the key research that needs to be done in the near future are all discussed. Permanent Snappy text:The synthesis, properties and applications of π-conjugated organic semiconductors especially those with fused rings are discussed in this tutorial review.

This is the accepted version of the paper.This version of the publication may differ from the final published version. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 Rechargeable lithium ion batteries (LIBs) have long been considered as the most effective energy-storage technology and dominated portable electronic market for over two decades. Permanent repository link1, 2 Based on the intercalation mechanism, state-of-the-art Li-ion technology can exhibit a theoretical specific energy of ~400 Wh/kg, such as LiCoO 2 /graphite system. 3 However, it is urgent to explore new chemistries and materials that can significantly increase the cell energy density, considering the future demand for electronic vehicles and large-scale energy storage plants. 4,5 Graphite, a widely used anode material for the current LIBs, has a theoretical capacity of only 372 mAh/g, given a fully intercalated LiC 6 compound, which is one of the limiting factors for achieving high energy density of the cell 6 . In order to overcome such technical bottleneck, considerable effort has been devoted to design and synthesise new anode materials with higher theoretical specific capacity, such as transition metal oxides (SnO 2 , Co 3 O 4 ,Fe 3 O 4 ), Sn and Si 7 . However, all these materials suffer from severe volume variation during charge-discharge cycling, which results in serious pulverisation of the electrodes, and thus, rapid capacity degradation. For instance, Si has a high specific capacity of 4200 mAh/g if fully lithiated to Li 4.4 Si, however, it also shows a large volume expansion up to 400%. Such volume expansion causes huge mechanical stress of the electrode, and therefore, severely limits the lifetime of Si anode. Although various strategies have been proposed to enhance the structural stability of Si-based materials, including carbon or polymer coating 8,9 , nano-structuring 10-12 and hierarchical hybridization, [13][14][15] it is still very challenge to overcome the issue of the inherent volume change of these materials during cycling.Transition metal dichalcogenides (TMD) MX 2 (M=Mo, Ti, V, and W, X=S or Se) 16,17 with the similar feature of layered structure as graphite could have great potential for alternative anode materials. In general, MX 2 has strong covalent bonds within layers and weak Van der Waals forces between layers, which provide ideal space for intercalation of lithium ions. For instance, MoS 2 has much larger spacing between neighboring layers (0.615 nm) than that of graphite (0.335 nm) and weak van der Waals forces between the layers, which, in principal, may make the Li + diffuse easier. However, certain electrochemical properties of MX 2 can only be achieved in their 1-D or 2-D nanostructured crystals because of the relatively high resistance for Li-ion transport in their bulk form. In addition, the electron conductivity of th...

No abstract

China's recent waves of internal migration, primarily rural to urban, reflect a rapidly urbanizing society undergoing a transition from a planned to a market economy. The author addresses two key questions: what access migrants have to urban housing and how migrant housing conditions compare with those of the locals. The main findings are based on citywide housing surveys and interviews conducted in Shanghai and Beijing, as well as results from official surveys. Interpretations of migrant housing patterns in urban China need to be linked with the country's unique institutional factors, particularly the circulating nature of migration, the existing household registration system, and the transitioning state of the urban housing market. Restricted access to urban housing, together with the temporary status for migrants, contributes to their poor housing conditions. Population mobility, primarily in the form of circulating migration, has increased significantly in China since 1983. A transient population of about three million now lives in both Beijing and Shanghai, according to the cities' official 1997 surveys of "floating population," 1 and the majority is regarded as labor migrants. Both surveys also show that about half a million migrants have lived in each city for more than three years. For many migrants, urban life is precarious-lack of shelter, low and uncertain earnings, and worsened living conditions. For some, city experience also is an eye opener-increased

The significant rise in labor mobility during the last two decades is a prominent feature of China's economic transition, reflecting a rapid process of industrialization and urbanization. Despite an impressive overall record of growth, income disparities between urban and rural areas, as well as regional imbalances, remain large. Primarily from rural to urban, much of the migratory flow takes place outside of the state plan and involves circular movements of rural labor in search of work to augment agricultural income. By the end of 2000 approximately 70 million rural migrants were working and living in urban areas according to official estimates. Nearly all of these people migrate without official change of household registration (hukou), although a small number manage to do so and achieve hukou change (permanent migration).This increasing level of mobility challenges the current population-management structure, as the hukou system still links residency with employment and social welfare. Most migrants continue to be regarded as temporary and have little chance of getting local hukou, no matter how long they have lived in the cities (often termed`temporary migrants', in this study I refer to them simply as`migrants'). Scholars agree that housing, an important element of urban amenities associated with hukou, remains difficult to attain for migrants (

This is the accepted version of the paper.This version of the publication may differ from the final published version. with an on/off ratio of 2.5 × 10 4 , which is among the best performance of the copolymers reported for the solution-processed organic field effect transistors (OFETs). The preliminary results indicate that PTZV-PT is a promising polymer material for applications in solution-processable OFETs. Permanent repository link

Over the past 20 years, organic field-effect transistors (OFETs) based on soluble polymers and conjugated oligomers have attracted enormous interest for the realization of organic electronic devices. 1 Pentacene as the benchmark material with a mobility beyond 1.0 cm 2 V -1 s -1 has been reported. 2 Despite the great progress in the exploration of functional organic materials for OFETs, 3 fundamental aspects of carrier transport, especially the role of solid-state packing, still remain unclear. 4 From the standpoint of bandwidth and the hopping theory of carrier conduction, a cofacial π stacking structure is expected to facilitate carrier transport. 4,5 However, most of the organic semiconductors with high mobilities have a herringbone structure which reduces the overlap. 6 On the other hand, the research work for OFETs has mainly focused on thin-film and bulk singlecrystal state. Study of micro-and nanomaterials, including fibers, ribbons, and wires, has only been recently reported because of the potential applications in integrated (opto) electronic devices due to many unique properties, such as flexibility, high photoconductivity, and nonlinear optical effects, etc. 7 Herein we present our studies of a new class of a high-performance OFET semiconductor based on perylo [1,12-b,c,d]thiophene (PET, Figure 1). The integration of a S atom into the polycyclic aromatic hydrocarbon (PAH) skeleton induces an extraordinary solid-state packing arrangement with the likelihood of double-channel superstructure, which is expected to permit effective charge transporting. Furthermore, we have grown its micrometer single-crystal wires by physical vapor transport and successfully applied them to transistors. The devices exhibit excellent performance with a high mobility up to 0.8 cm 2 V -1 s -1 .The oligothiophene and PAHs are among the most versatile and effective molecular scaffolds for organic functional materials. It is thus surprising that little effort has been devoted to exploiting sulfur heterocyclic PAHs in OFETs. We choose PET as an ideal system for investigating structure-property relationships among organic semiconductors because of its unique packing in single crystals ( Figure 1). Although its synthesis was first reported by Rogovik, 8 its electrical property is rarely studied. The crystal structure contains almost planar PET molecules stacked along the b-axis with interplanar distances of 3.47 Å, 9 in contrast to the sandwich herringbone packing of perylene crystals. Remarkably, marked S‚ ‚‚S short contacts (3.51 Å) were found between the neighboring columns related by an inversion center. The double-channel fashion is envisioned to be transformed into the facile establishment of a high-performance charge transport system.As a control result, we have first investigated the thin-film fieldeffect behavior of PET. Transistors have been fabricated on SiO 2 / Si substrate with octadecyltrichlorosilane (OTS) treatment, adopting a top-contact configuration. Only p-channel activity is observed for the device. It exhibits...

No abstract