Electron injection barrier and energy-level alignment at the Au/PDI8-CN2 interface via current-voltage measurements and ballistic emission microscopy

We probe electron transport across the Au/organic interface based on oriented thin films of the high-performance n-type perylene diimide semiconductor PDI8-CN 2 . To this purpose, we prepared organic-on-inorganic Schottky diodes, with Au directly evaporated onto PDI8-CN 2 grown on n-Si. Temperature-dependent current–voltage characteristics and complementary ballistic electron emission microscopy studies reveal that rectification at the Au/PDI8-CN 2 interface is controlled by a spatially inhomogeneous injection barrier, that varies on a length scale of tens of nanometers according to a Gaussian distribution with mean value about 0.94 eV and standard deviation of about 100 meV. The former gradually shifts to about 1.04 eV on increasing PDI8-CN 2 thickness from 5 nm to 50 nm. Experimental evidences and general arguments further allow to establish the energetics at the u/PDI8-CN 2 interface. Our work indicates injection-limited current flow in PDI8-CN 2 -based devices with evaporated Au electrodes. Furthermore, it suggests chemical reactivity of PDI8-CN 2 with both Au and Si, driven by the lateral isocyano groups.