University of Utah physicists have controlled an electrical current using electron spin, pointing toward an organic spin transistor. The researchers also demonstrated that fabricating efficient OLEDs may be more difficult than expected.
University of Utah physicists John Lupton and Christoph Boehme have successfully used electron spin to control an electrical current, an important step toward an organic spin transistor for ultrafast computing and other electronics applications. The experimentation merged organic semiconductor electronics and spintronics, believed to be the first time that fundamental, hands-on quantum mechanics has been done with organic LEDs.

This has immediate applications,” Lupton said. “Even with something as mundane as an OLED, you must understand what the spin lifetime is, because you have many carbon-based molecules that help low-spin orbit coupling, which means that spin is maintained. If you think about an OLED, where you inject positive and negative charges, each of these charges — plus and minus — carries spin either up, down, plus a half or minus a half, so you get four different combinations of spin when these electrons and holes recombine. In organic semiconductors, only the singlet configuration — one in four — that corresponds to the anti-parallel spin configuration decays radiatively. If the spin is long-lived, then you’ll get more triplets than singlets. Thus, the technique provides a direct spectroscopic window to understanding spin excitations in organic semiconductors. “All our present device concepts are based on the discovery of new degrees of freedom. We’ve demonstrated that the spin degree of freedom in organic semiconductors is well-worth exploiting.”
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