N-type doping of an electron-transport material by controlled gas-phase incorporation of cobaltocene

N-doping of an electron transport material with bis(cyclopentadienyl)-cobalt(II) (cobaltocene) is demonstrated using ultra-violet, X-ray, and inverse photoemission spectroscopies, and current-voltage measurements. Efficient n-doping is confirmed by a large shift of the Fermi level toward the unoccupied states of the host, and by a significant increase in current in cobaltocene-doped devices.