arXiv subjects

D. Kotowski

Publications and source records attributed to D. Kotowski.

2 recordsLinked to original sources

arXiv2006

$f^{-γ}$ Current Fluctuations in Organic Semiconductors: Evidence for Percolation

The $f^{-γ}$ sloped current noise power spectra, observed in organic semiconductors, have been interpreted within a {\em variable range hopping} mechanism of the fluctuations. The relative current noise power spectral density ${\cal S}(f)=S_I(f)/I^2$ exhibits a maximum at the {\em trap-filling transition} between the {\em ohmic} and the {\em space-charge-limited-current} regime [Phys. Rev. Lett., {\bf 95}, 236601, 2005]. Here, we discuss the electronic conditions determining the crossover from ohmic to space-charge-limited transport. These arguments shed further light on the need to adopt a {\em percolative} fluctuation picture to account for the competition between insulating and conductive phases coexisting at the {\em transition}, where small changes in the external bias lead to dramatic effects in the fluctuations.

cond-mat.dis-nn↗

arXiv2006

Space-Charge-Limited Current Fluctuations in Organic Semiconductors

Low-frequency current fluctuations are investigated over a bias range covering {\em ohmic}, {\em trap-filling} and {\em space-charge-limited current} regimes in polycrystalline polyacenes. The relative current noise power spectral density ${\cal S}(f)$ is constant in the {\em ohmic} region, steeply increases at the {\em trap-filling transition} region and decreases in the {\em space-charge-limited-current} region. The {\em noise peak} at the {\em trap-filling transition} is accounted for within a {\em continuum percolation model}. As the quasi-Fermi level crosses the trap level, intricate insulating paths nucleate within the ohmic matrix, determining the onset of non-equilibrium conditions at the interface between the insulating and conducting phase. The {\em noise peak} is written in terms of the free and trapped charge carrier densities.

cond-mat.dis-nn↗