Negative Temperature Dependence of Conductivity in Pentacene Thin Film Deposited on Au Electrode

We report the observation of an unusual charge transport in pentacene lm thermally evaporated on Au electrode. The transport through pentacene lm between the bottom Au and the top Ti/Au electrodes exhibited ohmic characteristics with a large current of 10 mA at 1.5 V, compared with the small space charge limited current in pentacene on SiO2. Particularly, the conductivity produced negative temperature dependence with activation energy of -5 meV until reaching a critical temperature, TC, above which the conductivity increased again with activation energy of 25 meV. The behavior can be rationalized by band-like transport below TC and phonon-assisted hopping above TC. KCI Citation Count: 3