Spin current relaxation time in thermally evaporated pentacene films

The spin current relaxation time (τ) in thermally evaporated pentacene films was evaluated with the spin-pump-induced spin transport properties and the charge current transport properties in pentacene films. Under an assumption of a diffusive transport of the spin current in pentacene films, the zero-field mobility and the diffusion constant of holes in pentacene films were experimentally obtained to be ∼8.0 × 10−7 m2/V s and ∼2.0 × 10−8 m2/s, respectively. Using those values and the previously obtained spin diffusion length in pentacene films of 42 ± 10 nm, the τ in pentacene films was estimated to be 150 ± 120 ns at room temperature. This estimated τ in pentacene films is long enough for the practical use as a spintronic material.