Electrical conductivity in metal/3,4,9,10-perylenetetracarboxylic dianhydride/metal structures

Samples comprising 1-μm-thick layers of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) sandwiched between top-most In contact and bottom-most Ag contact were synthesized on $n-Si(100)$ substrates. Current–voltage $(I–V)$ characteristics were measured on the structures with all the layers evaporated in sequence, and on the structures with air exposed PTCDA/In and Ag/PTCDA interfaces. The current transport in the structures fabricated without interruption of vacuum is controlled by the space charge and by the traps. Air exposure of the In/PTCDA interface introduces additional trap sites in the PTCDA layer, yielding the space-charge-limited current in the presence of traps, exponentially distributed in energy, and with a hopping transport mobility. Air exposure of the Ag/PTCDA interface introduces a discrete level of traps in addition to exponentially distributed traps.