Solution-processed organic spin–charge converter

Abstract

Conjugated polymers and small organic molecules are enabling new, flexible, large-area, low-cost optoelectronic devices, such as organic light-emitting diodes, transistors and solar cells. Owing to their exceptionally long spin lifetimes, these carbon-based materials could also have an important impact on spintronics, where carrier spins play a key role in transmitting, processing and storing information. However, to exploit this potential, a method for direct conversion of spin information into an electric signal is indispensable. Here we show that a pure spin current can be produced in a solution-processed conducting polymer by pumping spins through a ferromagnetic resonance in an adjacent magnetic insulator, and that this generates an electric voltage across the polymer film. We demonstrate that the experimental characteristics of the generated voltage are consistent with it being generated through an inverse spin Hall effect in the conducting polymer. In contrast with inorganic materials, the conducting polymer exhibits coexistence of high spin-current to charge-current conversion efficiency and long spin lifetimes. Our discovery opens a route for a new generation of molecular-structure-engineered spintronic devices, which could lead to important advances in plastic spintronics.

Spin-current injection and detection in κ-(BEDT-TTF)2Cu[N(CN)2]Br

“…Among these materials, conjugated polymers have been suggested to work as a spin-charge converter recently, 10,11 and further investigation of the spin-charge conversion in different organic materials will open new possibilities for the application of organic materials in spintronic devices. On the other hand, in the organic system, all the energy scales: correlation, electron-lattice coupling, and kinetic energy are small enough to compete with spin currents at low temperatures.…”

“…Firstly, it is a typical molecular salt and an organic band metal system, which is quite different from the polaron conductive conjugated polymers. 10,11 Secondly, since the physical and electrical properties of this organic family are well understood and highly controllable, it is easy to investigate and modulate the state of samples.…”

Spintronic detection of interfacial magnetic switching in a paramagnetic thin film of tris(8-hydroxyquinoline)iron(III)

“…To date organic spintronics research has focused on the physics of the spin injection and spin transport through the organic interlayer in OSV devices. Detection of spin transport through the OSEC layer has been done through a variety of techniques that include magneto-transport [3][4][5][6][7][8][9][10][11][12], inverse spin Hall effect [13,14], muon spin rotation (µSR) [15,16], and two-photon photoemission [17,18]. In most applications the spin control in the device has been achieved via the injected spinaligned carriers from conventional FM electrodes into the OSEC interlayer, in spite of the conductivity mismatch at their interface that poses a formidable barrier for spin injection [19].…”

Quantitative inverse spin Hall effect detection via precise control of the driving-field amplitude

“…The detection of spin pumping through the inverse spin Hall effect (ISHE) in semiconducting materials under ferromagnetic resonant (FMR) excitation of an adjacent ferromagnetic layer by microwave (MW) radiation is a recently developed technique for the study of spintransport phenomena and spin-orbit coupling (SOC) effects in various materials [1][2][3][4][5], in particular in materials with weak SOC, such as organic semiconductors. As the magnitude of the ISHE response scales linearly with the strength of the MW radiation field [3][4][5][6][7][8], quantitative ISHE experiments which, for instance, are needed to test fundamental theories of charge free spin-injection into organic semiconductors [9] or the nature of spin transport in the latter [10], require a precise knowledge of the strength of the MW radiation amplitude B 1 .…”

“…As the magnitude of the ISHE response scales linearly with the strength of the MW radiation field [3][4][5][6][7][8], quantitative ISHE experiments which, for instance, are needed to test fundamental theories of charge free spin-injection into organic semiconductors [9] or the nature of spin transport in the latter [10], require a precise knowledge of the strength of the MW radiation amplitude B 1 . Most studies involving ISHE experiments derive B 1 from estimates that are based on the MW power applied to the resonator or waveguide structure.…”