International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

Organic photovoltaics (OPV) have the advantage of possible fabrication by energy-efficient and cost-effective deposition methods, such as solution processing. Solvent additives can provide fine control of the active layer morphology of OPVs by influencing film formation during solution processing. As such, solvent additives form a versatile method of experimental control for improving organic solar cell device performance. This review provides a brief history of solution-processed bulk heterojunction OPVs and the advent of solvent additives, putting them into context with other methods available for morphology control. It presents the current understanding of how solvent additives impact various mechanisms of phase separation, enabled by recent advances in in situ morphology characterization. Indeed, understanding solvent additives' effects on film formation has allowed them to be applied and combined effectively and synergistically to boost OPV performance. Their success as a morphology control strategy has also prompted the use of solvent additives in related organic semiconductor technologies. Finally, the role of solvent additives in the development of next-generation OPV active layers is discussed. Despite concerns over their environmental toxicity and role in device instability, solvent additives remain relevant morphological directing agents as research interests evolve toward nonfullerene acceptors, ternary blends, and environmentally sustainable solvents.

Solvent Additives: Key Morphology‐Directing Agents for Solution‐Processed Organic Solar Cells

Paper, as a flexible, low-cost, lightweight, tailorable, environmental-friendly, degradable, and renewable material, is emerging in electronic devices Especially, many kinds of paper-based (PB) sensors have been reported for wearable applications in recent years Among them, the PB gas, humidity, and strain sensors are widely studied for monitoring gas, humidity, and strain from the human body and the environment However, gas, humidity, and strain often coexist and interact, and the paper itself is hydrophilic and flexible, resulting in that it is still challenging to develop high-performance PB sensors specialized for gas, humidity, and strain detections Therefore, it is necessary to summarize and discuss them systematically In this review, we focus on summarizing the state-of-art studies of the PB gas, humidity, and strain sensors Specifically, the fabrications (electrodes and sensing materials) and applications of PB gas, humidity, and strain sensors are summarized and discussed The current challenges and the potential trends of PB sensors for gas, humidity, and strain detections are also outlined This review not only can help readers to understand the development status of the PB gas, humidity, and strain sensors but also is helpful for readers to find out and solve the problems in this field through comparative reading

Paper-Based Sensors for Gas, Humidity, and Strain Detections: A Review.

Conjugated polymer chains have many degrees of conformational freedom and interact weakly with each other, resulting in complex microstructures in the solid state. Understanding charge transport in such systems, which have amorphous and ordered phases exhibiting varying degrees of order, has proved difficult owing to the contribution of electronic processes at various length scales. The growing technological appeal of these semiconductors makes such fundamental knowledge extremely important for materials and process design. We propose a unified model of how charge carriers travel in conjugated polymer films. We show that in high-molecular-weight semiconducting polymers the limiting charge transport step is trapping caused by lattice disorder, and that short-range intermolecular aggregation is sufficient for efficient long-range charge transport. This generalization explains the seemingly contradicting high performance of recently reported, poorly ordered polymers and suggests molecular design strategies to further improve the performance of future generations of organic electronic materials.

http://absimage.aps.org/image/MAR14/MWS_MAR14-2013-020288.pdf

A general relationship between disorder, aggregation and charge transport in conjugated polymers

Flexible sensors have the potential to be seamlessly applied to soft and irregularly shaped surfaces such as the human skin or textile fabrics. This benefits conformability dependant applications including smart tattoos, artificial skins and soft robotics. Consequently, materials and structures for innovative flexible sensors, as well as their integration into systems, continue to be in the spotlight of research. This review outlines the current state of flexible sensor technologies and the impact of material developments on this field. Special attention is given to strain, temperature, chemical, light and electropotential sensors, as well as their respective applications.

Flexible Sensors—From Materials to Applications

Flexible resistive switching memory device is an excellent option for future high density memory and flexible electronics applications. Here, bipolar resistive switching behavior in Al/HfO x /Au resistive random access memory (RRAM) devices fabricated on ultra-flexible polyimide substrates is demonstrated. These devices can be programmed at read-write voltages as low as 0.18 V with on-off current ratios (I on /I off ) of 18, resistance ratio of ∼41 in high and low resistance states (HRS & LRS) and stable set and reset voltages over 16 cycles of operation. The mechanism of resistive switching in these devices is explained with help of filament formation and rupture process due to oxygen vacancy and oxygen ions migration. Ohmic conduction prevails in HRS and LRS whereas conduction mechanism is dominated by space charge limited conduction (SCLC). These flexible RRAM devices could be an excellent option for future high density memory applications.

Low voltage resistive switching behavior of Al/HfO x /Au structure on ultra-flexible polyimide substrate

Inverter circuits based on neat TIPS-pentacene and TIPS-pentacene: polystyrene blend organic field-effect transistors (OFETs) with external resistive load has been studied. Resistive loads of 28 ΜΩ, 40 ΜΩ, 68 ΜΩ and 108 ΜΩ were used to study the inverter transfer characteristics. Transfer characteristics of both types of inverters are improved with increasing load resistance. Inverter with a representative OFET with neat TIPS-pentacene shows a DC voltage gain of −6.9, swing of 40 V, and static power dissipation of 9.5 μW with load of 108 ΜΩ and 50 V power supply. Similarly, inverter with a representative TIPS-pentacene: polymer blend OFET shows a DC voltage gain of −8.7, swing of 44 V, and static power dissipation of 10.2 μW with the same load. For both neat TIPS-pentacene and TIPS-pentacene: polymer blend inverters, maximum DC gain and voltage swing are achieved with highest value of resistive load. However, switching thresholds near V DD /2 are obtained with moderate resistive loads.

TIPS-pentacene:Polymer blend inverters with improved gain

I-V characteristic is one of the important results produced by a device simulator. In this article, a novel and interactive matrix based algorithm is presented to draw the device structure in 2-D or 3-D style and to plot the I-V characteristic of the device for user specified doping and biasing conditions. Algorithm creates 2-D or 3-D matrix of the device from device description mentioned by the user. This device matrix undergoes many different operations, and various mathematical computations are performed, using which I-V characteristic is plotted. This approach gives a novel idea of basic device level tool development. The students and device level engineers can find this work useful which offers them an interactive and instant way to draw I-V characteristics of the device. The algorithm implementation is modular and matrix based, which is done using MATLAB®.

Deepak Bharti

Papers

Low voltage resistive switching behavior of Al/HfO x /Au structure on ultra-flexible polyimide substrate

TIPS-pentacene:Polymer blend inverters with improved gain

Design of a Static Current Simulator Using Device Matrix Approach