Saturday, October 19, 2013

Record high electron and hole mobility for organic solar cells, transistors and other optoelectronic applications

I think everyone agrees - charge transport is a key parameter of any electronic device, because it defines the material's ability to conduct the electrical current. In other words, charge carrier mobility, in particular electron and hole mobility, must be sufficiently high in order for electronic devices to reach specific performance requirements, say high power conversion efficiency for solar cells or high on/off ratio and frequency for field effect transistors, or high brightness of organic light emitting diodes etc.

But, if the charge transport is so important, let me ask you then, how come that I so rarely see the scientific papers published with such keywords as "charge transport", "carrier mobility" in academic journals? Nature or Science journals nearly never publishes articles about charge transport (maybe once a year or so). I believe this needs to change, because no improvements in charge transport - no improvements in performance of electronic devices.

Personally, my main academic focus is on charge transport and mechanisms of electrical conduction. My last ten years I have been working on trying to understand the electron and hole movement in organic semiconductors better. And let me tell you what I think about this research topic: not so many people actually even know how to measure charge carrier mobility in disordered organic films reliably! There are so many reasons why classical techniques (current-voltage or I-V is one of them) can not be applied in these materials. And naturally, the lack of techniques and the complexity of the charge transport phenomena scares scientists away from it.

But this can change, the significance of charge transport can be brought back from the cellar into the daylight. I believe that the accelerated progress is only possible when issues are being addressed through understanding and not just by poking in the dark on random and hoping to synthesize materials with good mobility for instance.

Lately, I have been developing novel techniques, such as Flash Photovoltage (FPV) and Metal-Insulator-Semiconductor Charge Extraction by Linearly Increasing Voltage (MIS-CELIV). These techniques allow to study the charge transport in disordered (organic and inorganic) semiconductors and electronic devices much more reliably than any technique previously known (including photo-CELIV). For instance, FPV is perfect for actual and operational organic solar cells or light emitting diodes. MIS-CELIV is perfect for quantifying the electron and hole mobility in novel and unknown organic materials.

So, folks stay tuned, I have submitted the papers and hopefully that rotten anonymous academic peer-review process will not delay them for too long.

And, if you have arrived to this page as a results of Google search and hoping to find here those "record high mobility" values, you just have to wait for those "records" - wont be too long anymore :)

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