ADVERTISEMENT

Developing Organic Semiconductor Crystals For Circuits, Displays, And Bioimplantable Sensors

Flexible electronic devices based on organic semiconductors are believed to be a high potential candidate for the next generation modern electronics. From wearable smart sensors to flexible displays, organic electronics have shown promising development in the last two decades.

Among different processing method, solution shearing is a high potential deposition method to fabricate organic electronics over a large area. In this method, the uniformity and crystallinity of the deposited organic thin film is very sensitive to the shearing speed. It can be expected that if the shearing speed is too fast, unwanted voids will present in the film and which will make the large-scale device integration very difficult. On the other hand, if the shearing speed is too slow, intensive multiple nucleations will present along the meniscus line and thus high grain boundary density will result.

ADVERTISEMENT

These grain boundaries will unavoidable hurt the carrier transfer mobility while they are hopping from one grain to another. Furthermore, both of these two scenarios will significantly affect the repeatability of fabrication and overall uniformity of the organic devices especially for the in planar devices such as field effect transistors. In this work, we tried to address this issue by using the Marangoni-effect assisted bar coating method to deposit the C8-BTBT organic crystals. Compare with the traditional method with only single solvent, the dual solvent Marangoni-effect assisted bar coating approach can support five times faster shearing speed up to 1000 mm/s without hurting the quality of the organic thin film.

By carefully controlling the solvent composition and the temperature gradient in the solute, we can use the Marangoni-effect induced by the differences in surface tension to provide extra organic molecules to the meniscus line. This extra source of molecules allows us to shear the solution in a quicker way without causing the opening voids due to insufficient supply of the organic molecules. More importantly, the magnitude of such Marangoni-effect can be varied by carefully controlling the temperature gradient and composition of mixed solvents. As this effect is highly localized at the liquid, solid and air interface, the solute outside the meniscus line will not be affected. With the high shearing speed, we found the deposited organic crystals are actually under both compressive and tensile strain depending on their orientations.

We found that the stain up to 0.7% can be observed in the C8-BTBT crystals deposited under 1000 mm/s. These findings demonstrate the great potentials in modifying the crystallinity of these organic semiconductors which is holding together by the van der Waals force. It is believed that this method can be further utilized to adjust the carrier mobility and other electrical properties of the organic thin films.

It is believed that the compressive strain in the right direction can enhance the carrier transfer in between the organic molecules. Another interesting research direction is to perform another solution shearing onto the strained semiconductor and see whether will the intrinsic strain in the crystal be released. These investigations will help us to understand the strain forming and releasing mechanisms in the solution processed organic semiconductors, and how we can utilize it to modify the performance of the devices over a large area.

ADVERTISEMENT

Our studies on other organic semiconductors are undergoing, we are targeting in coming up with an universal fabrication approach to manipulate the strain effect in the solution processed organic semiconductors.

This study, Marangoni-Effect-Assisted Bar-Coating Method for High-Quality Organic Crystals with Compressive and Tensile Strains was recently published in the journal Advanced Functional Materials.

Comments

READ THIS NEXT

Pincher Bug (Earwig) Bite And Pictures

Earwigs are insects that fall under the order Dermaptera. Containing about 2,000 individual species spread over 12 families, earwigs are one of […]

Designing Better Lithium-ion Batteries  

With the increase in world population and quality living, energy has become a significant part of our daily life. Currently, […]

Ocean Acidification And Its Impact On Marine Environments

Recently, news such as the story of a polar bear desperately reaching for an ice floe and a global-scale coral […]

On The Shoulders Of Giants, Part 2: Stewart Wolf And The Pharmacology Of Placebos

In comparison to Henry Beecher’s much-cited paper, “The Powerful placebo,” of 1955 (1), Stewart Wolf’s paper, “The pharmacology  of placebos,” of […]

A New Infiltration Model For Short-Duration Rainfall

Global warming enables atmosphere to hold more water and accelerates the global water cycle. The warmer air provides more moisture […]

Addressing The Financial Market Impact Of Declining Demand For Fossil Fuels

At the 2015 United Nations Climate Change Conference in Paris there was agreement — termed COP21 and then COP23 for […]

Water Reuse And The Circular Economy

Water is essential for human survival and well-being and plays an important role in many sectors of the economy. However, […]

Science Trends is a popular source of science news and education around the world. We cover everything from solar power cell technology to climate change to cancer research. We help hundreds of thousands of people every month learn about the world we live in and the latest scientific breakthroughs. Want to know more?