Work function reduction by a redox-active organometallic sandwich complex

• We examine via DFT calculations the impact of strongly reducing metallocene complexes on the work function of gold and ITO.
• The IrCpCp* monomer can lower the work functions of both surfaces by about 1.2–1.3 eV, while the dimer has much lower effect.
• The large work function change induced by IrCpCp* monomer comes from a large interface dipole due to charge transfer.

We have investigated, at the density functional theory level, the geometric and electronic structures of the pentamethyliridocene (IrCpCp*) monomer and dimer adsorbed on the Au(111) and indium tin oxide (ITO) (222) surfaces, as well as their impact on the work functions. Our calculations show that the adsorption of a monomer lowers the work function of ITO(222) by 1.2 eV and Au(111) by 1.2–1.3 eV. The main origin for this reduction is the formation of an interface dipole between the monomer and the substrate via charge transfer. Dimer adsorption as well as adsorption of possible byproducts formed from dimer bond-cleavage in solution, show a lesser ability to lower the work function.