'Inverse spin Hall effect' works in several organic semiconductors
Apr 18, 2016 – By showing that a phenomenon dubbed the “inverse spin Hall effect” works in several organic semiconductors – including carbon-60 buckyballs – University of Utah physicists changed magnetic “spin current” into electric current. The efficiency of this new power conversion method isn’t yet known, but it might find use in future electronic devices including batteries, solar cells and computers.
University of Utah physicists Z. Valy Vardeny and Christoph Boehme published a new study in Nature Materials demonstrating that a range of organic semiconductors can be used to convert a so-called magnetic spin current into electric current. They don’t yet know the efficiency of this power-conversion method, but say it has possible future uses in future solar cells, batteries and electronic devices like computers and cell phones. Photo credit: Lee J. Siegel, University of Utah
“This paper is the first to demonstrate the inverse spin Hall effect in a range of organic semiconductors with unprecedented sensitivity,” although a 2013 study by other researchers demonstrated it with less sensitivity in one such material, says Christoph Boehme, a senior author of the study published April 18 in the journal Nature Materials.
“The inverse spin Hall effect is a remarkable phenomenon that turns so-called spin current into an electric current. The effect is so odd that nobody really knows what this will be used for eventually, but many technical applications are conceivable, including very odd new power-conversion schemes,” says Boehme, a physics professor.
His fellow senior author, distinguished professor Z. Valy Vardeny, says that by using pulses of microwaves, the inverse spin Hall effect and organic semiconductors to convert spin current into electricity, this new electromotive force generates electrical current in a way different than existing sources.
Coal, gas, hydroelectric, wind and nuclear plants all use dynamos to convert mechanical force into magnetic-field changes and then electricity. Chemical reactions power modern batteries and solar cells convert light to electrical current. Converting spin current into electrical current is another method.
Scientists already are developing such devices, such as a thermoelectric generator, using traditional inorganic semiconductors. Vardeny says organic semiconductors are promising because they are cheap, easily processed and environmentally friendly. He notes that both organic solar cells and organic LED (light-emitting diode) TV displays were developed even though silicon solar cells and nonorganic LEDs were widely used.
Vardeny and Boehme stressed that the efficiency at which organic semiconductors convert spin current to electric current remains unknown, so it is too early to predict the extent to which it might one day be used for new power conversion techniques in batteries, solar cells, computers, phones and other consumer electronics.
“I want to invoke a degree of caution,” Boehme says. “This is a power conversion effect that is new and mostly unstudied.”
Boehme notes that the experiments in the new study converted more spin current to electrical current than in the 2013 study, but Vardeny cautioned the effect still “would have to be scaled up many times to produce voltages equivalent to household batteries.”
The new study was funded by the National Science Foundation and the University of Utah-NSF Materials Research Science and Engineering Center. Study co-authors with Vardeny and Boehme were these University of Utah physicists: research assistant professors Dali Sun and Hans Malissa, postdoctoral researchers Kipp van Schooten and Chuang Zhang, and graduate students Marzieh Kavand and Matthew Groesbeck.