Since they emerged in the 1970s, microprocessors have been making inroads into every industry. Driven by incessant research and development by giant global corporations, microprocessor technology has been growing in leaps and bounds. The number of transistors that can be packed into a microprocessor of a given size has been doubling every two years. As a result, the cost per transistor within the microprocessor has been dropping.
The net effect is every new generation of microprocessors provides a lot more processing power for a relatively small increase in price. This has led to the microprocessor becoming so ubiquitous over the last couple of decades that there is hardly any facet of human existence that is not touched by it.
However, the more technology advances, the more challenging each new step becomes. Semi-conductor technology, on which the microprocessor industry is founded, will soon come up against the limits imposed by the fundamental nature of the materials used, such as silicon. Once that happens, maintaining the current rates of growth in processing power would no longer be possible. In anticipation of this, the global technology industry is looking for alternate ways to maintain innovation and growth.
One such area that has been receiving a lot of attention has been the niche of flexible electronics. Work done on Organic Semiconductors at academic labs has encouraged designers and engineers to try and create products such as low-cost radio-frequency identification (RFID) tags, flexible displays, wearable electronics, even working electronic circuits printed on paper. Turning these seemingly science-fiction concepts into reality calls for using organic semiconducting materials such as Pentacene rather than the inorganic substances such as silicon that have been used in conventional microprocessors.
Organic semiconducting materials share the property of semi-conductivity with their inorganic counterparts, but the way that charge particles are transported within them is different. They are also markedly different in terms of their optical, electronic, chemical and structural properties. Moreover, they are much more sensitive to environmental variations.
Knowledge of inorganic semiconducting materials, therefore, will only be of limited use in understanding the how and why of organic semiconductor behaviour. Theories developed through the study of crystalline semiconductors, for instance, might be of very limited relevance to understanding the source of charges and their transportation in organic semiconductors.
While a lot of research has been done on organic semiconductors, the main thrust so far has been on applied research. Aimed at technological advancement for fabrication of high performance devices, this has resulted in the ability to manufacture stable products in a cost-effective manner. In contrast, basic research into organic semiconductors has been lacking. This has led to a limited understanding of the fundamentals, with conflicting theories on why organic semiconductors behave the way they do. Bridging this gap calls for extensive and exhaustive efforts in basic research.
At the IITB-Monash Research Academy, research scholar Akash Nigam has been making significant strides in this direction. Working under the guidance of Prof. Ramgopal Rao of IIT Bombay and Prof. Malin Premaratne of Monash university, Akash has been studying charge carrier transport within organic semiconductors. Aimed at advancing the understanding of the fundamentals of charge statistics and dynamics, the study has two closely linked components.
The first part focuses on understanding how the mobility of charges is affected by strain. This is particularly relevant to flexible electronics, since little is known about how and why the behaviour of a semiconductor will change when it is bent. Understanding the effects of strain is of critical importance in developing applications, since one of the advantages of organic semi-conductors is their flexibility. In large devices like flexible displays, for instance, this knowledge will help in two ways. On the one hand, the effect of twisting or curling on charge transport can be minimized. On the other, the effect of strain can be capitalized on in order to boost performance.
The second part of the study aims to understand how introducing a charge into an organic semiconductor affects its ability to store an electric charge (i. e. capacitance) at different voltages. Knowledge of the correlation between the magnitude of the charge introduced and capacitance-voltage profile of a device is essential to determine the charge density inside the device. Since capacitance-voltage profiling is the prevalent method for determining the charge density in a semiconductor, the results of the study would prove invaluable to the worldwide scientific community. It will be a powerful tool for designing and refining semiconductor-based devices such as solar cells, transistors, light-emitting diodes (LED) etc.
"I find basic research exciting because it helps find answers to fundamental questions," says Akash. "The results of the kind of work that we do might not bring immediate returns by way of new technology or products. However, we are contributing towards expanding the knowledge base of the worldwide scientific community. That is the foundation on which the semiconductor industry, which constitutes 10% of global GDP, is built"
Akash's views are in line with the vision that led to the founding of the IITB-Monash Research Academy. Says Prof. Mohan Krishnamoorthy, CEO, IITB-Monash Research Academy, "The IITB-Monash Research Academy was conceived as a unique model for how two leading, globally focussed academic organisations can come together in the spirit of collaboration to deliver solutions to challenging questions facing industry and society."
The IITB-Monash Research Academy is a Joint Venture between the IIT Bombay, India and Monash University, Australia. Opened in 2008, the IITB-Monash Research Academy operates a graduate research program located in Mumbai that aims at enhancing research collaborations between Australia and India. Students study for a dually-badged PhD from both institutions, and spend time during their research in both India and Australia.
Research scholar: Akash Nigam, IITB-Monash Research Academy
Project title: FUnderstanding the charge carrier transport along the grain and grain boundary networks of organic semiconductors.abrication and Experimental Characterization of Spin polarized light sources
Supervisors: Ramgopal Rao, Malin Premaratne
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