  Plasmonic Au-Pt core-shell heterojunctions were prepared as nanoemitters at
pre-structured porous SiO2/Si interfaces. Silicon templates were obtained by
oscillatory photocurrent cycles in fluoride containing solutions. Local
formation of noble metal heterocontacts was realized by electrodeposition of i)
Pt nuclei at Si pore tips, ii) spherical Au deposits on Pt nuclei and iii)
protective Pt shells. Enhanced light absorption of these Au-Pt/SiO2/Si
nanoarchitectures is deduced from Mie scattering analysis and Finite Difference
Time Domain simulations. Operation of the photoelectrodes in I-/I3- redox
electrolytes confirms the potential advantage of the concept over monometallic
Pt emitter interfaces. Efficiencies for solar light to energy conversion up to
8.7% were already obtained. Further optimization of the device is discussed in
terms of interface state formation at the SiO2/Si boundary and Schottky-type
junction properties.
