Deepak Bharti

Bio: Deepak Bharti is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Pentacene & Field-effect transistor. The author has an hindex of 9, co-authored 36 publications receiving 237 citations. Previous affiliations of Deepak Bharti include Malaviya National Institute of Technology, Jaipur & Birla Institute of Technology and Science.

Solution-Processed Organic Field-Effect Transistors with High Performance and Stability on Paper Substrates.

Abstract: High-performance operationally stable organic field-effect transistors were successfully fabricated on a PowerCoat HD 230 paper substrate with a TIPS-pentacene:polystyrene blend as the active layer and poly(4-vinylphenol)/HfO2 as the hybrid gate dielectric. The fabricated devices exhibited excellent p-channel characteristics with a maximum and av field effect mobility of 0.44 and 0.22(±0.11) cm2 V–1 s–1, respectively, av threshold voltage of 0.021(±0.63) V, and current on–off ratio of ∼105 while operating at −10 V. These devices exhibited remarkable stability under effects of gate bias stress and large number of repeated transfer scans with negligible performance spread. In addition, these devices displayed very stable electrical characteristics after long exposure periods to humidity and an excellent shelf life of more than 6 months in ambient environment. Thermal stress at high temperatures however deteriorates the device characteristics because of the generation and propagation of cracks in the active ...

High Performance and Electro-Mechanical Stability in Small Molecule: Polymer Blend Flexible Organic Field-Effect Transistors

Abstract: High-performance solution processed flexible organic field-effect transistors with 6,13(bis-triisopropylsily-lethynyl) pentacene and polystyrene blend are demonstrated with high electro-mechanical stability. For −5 V operation, field-effect mobility up to 1.1 cm $^{2}~\text{V}^{\mathrm {-1}}~\text{s}^{\mathrm {-1}}$ and threshold voltage as low as −0.1 V were obtained with high current on–off ratios of $\sim 10^{5}$ due to high quality dielectric–semiconductor interface developed during solvent evaporation. Stable electrical characteristics were achieved with increasing duration of mechanical strain, and after multiple cycles of tensile and compressive strain. Drain current decay of 10%, very large trapping time of $\sim 10^{8}$ s, and a very small threshold voltage shift of 0.3 V were observed during bias stress of 1 h, signifying low charge carrier trapping and a high quality of dielectric–semiconductor interface, which was retained largely after two days of continuous tensile strain. Moreover, after 100 cycles of tensile and compressive strain, the corresponding shift in threshold voltage due to bias stress was still $\sim 0.5$ V. Overall, a high performance and stability were demonstrated under collective effects of mechanical and electrical stress.

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

Abstract: 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.

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

Abstract: 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

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

Abstract: 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.

Flexible Sensors—From Materials to Applications

Abstract: 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.