Reported is the observation of dark spin-dependent electrical conduction in a Schottky barrier diode with pentacene (PSBD) using electrically detected magnetic resonance at room temperature. It is suggested that spin-dependent conduction exists in pentacene thin films, which is explored by examining the anisotropic linewidth of the EDMR signal and current density-voltage (J-V) measurements. The EDMR spectrum can be decomposed to Gaussian and Lorentzian components. The dependency of the two signals on the applied voltage was consistent with the current density-voltage (J-V) of the PSBD rather than that of the electron-only device of Al/pentacene/Al, indicating that the spin-dependent conduction is due to bipolaron formation associated with hole polaronic hopping processes. The applied-voltage dependence of the ratio of intensity of the Gaussian line to the Lorentzian may infer that increasing current density should make conducting paths more dispersive, thereby resulting in an increased fraction of the Gaussian line due to the higher dispersive g-factor.

A straightforward method for a variable frequency electron spin resonance/electrically detected magnetic resonance (ESR/EDMR) spectroscopy using a C-band microwave cavity equipped with waveguide windows is presented. The method enables us to perform quasi-continuous multiple resonance frequency (MF-ESR/EDMR) experiments for electronic devices. The C-band microwave circuitry was selected because of larger available sample volume than that for conventional X-band one. All the measurements were performed using a combined sample of 2,2-diphenyl-1-picrylhydrazyl/ pn-junction Si diode. The present simple MF-ESR/EDMR method will be useful for the characterization of electronic and optoelectronic devices.

Pauli spin blockade associated with bipolaron formation from positively charged mobile and trapped polarons in a regioregular poly(3‐hexylthiophene‐2,5‐diyl) (RR‐P3HT) Schottky barrier diode is detected using electrically detected magnetic resonance (EDMR) spectroscopy. This is the first experimental observation of bipolaron formation from positively charged mobile and trapped polarons in the space‐charge‐limited conduction regime in a polymer semiconductor. It is inferred that carrier traps exist in the disordered regions at the crystalline grain boundaries in RR‐P3HT. Furthermore, EDMR measurements under various constant‐current conditions suggest that shallow and deep traps have distinguishable g‐values.

Spin-dependent space-charge-limited carrier conduction in a Schottky barrier diode using polycrystalline p-type π-conjugated molecular pentacene is explored using multiple-frequency electrically detected magnetic resonance (EDMR) spectroscopy with a variable-angle configuration. The measured EDMR spectra are decomposed into two components derived, respectively, from mobile and trapped positive polarons. The linewidth of the EDMR signal for the trapped polarons increases with increasing resonance magnetic field for an in-plane configuration where the normal vector of the device substrate is perpendicular to the resonance magnetic field, while it is independent of the field for an out-of-plane configuration. This difference is consistent with the pentacene arrangement on the device substrate, where pentacene molecules exhibit a uniaxial orientation on the out-of-substrate plane. By contrast, the mobile polarons do not show anisotropic behavior with respect to the resonance magnetic field, indicating that the anisotropic effect is averaged out owing to carrier motion. These results suggest that the orientational arrangements of polycrystalline pentacene molecules in a nano thin film play a crucial role in spin-dependent electrical conduction.

No abstract

No abstract

No abstract