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

Investigation of resistive switching in PVP and ultra-thin HfOx based bilayer hybrid RRAM

Influence of molecular weight of polymer dielectric on the photo-response of solution-processed OFETs

A different strategy to form dielectric thin films using atomic layer deposition is proposed, where the dielectric stack consists of three layers in which the middle layer is deposited at a higher temperature than the top and bottom layer. This multi-temperature dielectric stack in metal-insulator-metal capacitor offers improved electrical properties compared to a dielectric film deposited at a single temperature. A multilayer 40 nm thick Al2O3 deposited with temperature and thickness sequence of 80 °C - 10 nm, 150 °C - 20 nm, and 80 °C - 10 nm offers reduced leakage current density by more than one order of magnitude compared to that for a 40 nm Al2O3 deposited at 150°C, and offers higher capacitance density compared to that for 40 nm Al2O3 deposited at 80 °C, and low values of voltage coefficients of capacitance. The changes in the capacitance density and leakage current are found to be strongly dependent on the various roughness values in the devices.

Improved properties of MIM capacitors using ALD Al2O3 by multi-temperature technique

Organic field effect transistors (OFETs) have been widely explored for their popular applications in flat panel displays and various kinds of affordable sensors. The overall performance of the device depends on the quality of semiconductor-dielectric interface, and degree of crystalline order in the active layer, close to the above said interface. In the special league of solution processed OFETs, semicondutor: polymer blends have been reported as one of the best possible ways to achieve an intimate, uniform and defect free semiconductor-dielectric interface in a single step. In addition, degree of crystalline order can be further ameliorated through solvent vapor annealing (SVA), which essentially controls the evaporation time of the solvent.

Performance enhancement in TIPS-pentacene:PS blend organic field effect transistors by solvent vapor annealing

Physics-based two-dimensional numerical simulations are performed to analyze the device characteristics of tri-isopropylsilylethynyl (TIPS)-pentacene organic thin-film transistor (OTFT) fabricated using drop-casting technique. Further, using simulation technique enabling calibration this paper also presents the systematic study of the impact of active layer (TIPS-pentacene) thickness on device characteristics. The extracted parameters such as electric field intensity, current density, current On/Off ratio, and mobility exhibit variation with scaling down in active layer thickness from 500 to 100 nm. The study also revealed that Off current and On/Off current ratio (IOn/IOff) is highly dependent on the thickness of the semiconductor layer. Furthermore, the highest value of IOn/IOff is obtained at 100-nm thickness of TIPS-pentacene, which can be used for various fast-switching applications in digital circuits. Simulated results are not only reasonably matching with experimental results but also provide insight on charge transportation at the semiconductor-dielectric interface and in the bulk of TIPS-pentacene layer.

Deepak Bharti

Papers

Investigation of resistive switching in PVP and ultra-thin HfOx based bilayer hybrid RRAM

Influence of molecular weight of polymer dielectric on the photo-response of solution-processed OFETs

Improved properties of MIM capacitors using ALD Al2O3 by multi-temperature technique

Performance enhancement in TIPS-pentacene:PS blend organic field effect transistors by solvent vapor annealing

Performance Investigation of Organic Thin Film Transistor on Varying Thickness of Semiconductor Material: An Experimentally Verified Simulation Study