One step self-aligned multilayer patterning process for the fabrication of organic complementary circuits in combination with inkjet printing

Recent development of solution processable organic semiconductors delineates the emergence of a new generation of air-stable, high performance p- and n-type materials. This makes it indeed possible for printed organic complementary circuits (CMOS) to be used in real applications. The main technical bottleneck for organic CMOS to be adopted as the next generation organic integrated circuit is how to deposit and pattern both p- and n-type semiconductor materials with high resolutions at the same time. It represents a significant technical challenge, especially if it can be done for multiple layers without mask alignment. In this paper, we propose a one-step self-aligned fabrication process which allows the deposition and high resolution patterning of functional layers for both p- and n-channel thin film transistors (TFTs) simultaneously. All the dimensional information of the device components is featured on a single imprinting stamp, and the TFT-channel geometry, electrodes with different work functions, p- and n-type semiconductors and effective gate dimensions can all be accurately defined by one-step imprinting and the subsequent pattern transfer process. As an example, we have demonstrated an organic complementary inverter fabricated by 3D imprinting in combination with inkjet printing and the measured electrical characteristics have validated the feasibility of the novel technique. © 2012 Elsevier B.V. All rights reserved.

Fabrication of excitonic luminescent inorganic-organic hybrid nano- and microcrystals

Inorganic-organic (IO) hybrid nano- and microcrystals are fabricated by a low-cost, environmentally friendly and easily scaled-up route. Lead(II) iodide (PbI 2) nano/microcrystals are obtained by solvothermal techniques and subsequent IO hybrid (C 12H 25NH 3) 2PbI 4 crystals are produced by intercalation of the organic moiety. The hexagonally shaped crystals obtained range in size from 20 nm to ∼7 μm. Sequential stacking of inorganic/organic layers in these IO hybrid crystals results in strong room-temperature exciton photoluminescence, wherein the excitons are confined within the inorganic sheets. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Pollutant flushing with natural displacement ventilation

We examine the time taken to flush pollutants from a naturally ventilated room. A simple theoretical model is developed to predict the time taken for neutrally-buoyant pollutants to be removed from a room by a flow driven by localised heat inputs; both line and point heat sources are considered. We show that the rate of flushing is a function of the room volume, vent areas ( A) and the distribution, number (n) and strength (B) of the heat sources. We also show that the entire problem can be reduced to a single parameter ( μ) that is a measure of the vent areas, and a dimensionless time ( τ) that is a function of B, V and μ. Small-scale salt-bath experiments were conducted to measure the flushing rates in order to validate our modelling assumptions and predictions. The predicted flushing times show good agreement with the experiments over a wide range of μ. We apply our model to a typical open plan office and lecture theatre and discuss some of the implications of our results. © 2005 Elsevier Ltd. All rights reserved.

π-Conjugated molecules with fused rings for organic field-effect transistors: design, synthesis and applications

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.