Metal‐Insulator‐Semiconductor Anodes for Ultrastable and Site‐Selective Upconversion Photoinduced Electrochemiluminescence

Photoinduced electrochemiluminescence (PECL) allows the electrochemically assisted conversion of low‐energy photons into high‐energy photons at an electrode surface. This concept is expected to have important implications, however, it is dramatically limited by the stability of the surface, impeding future developments. Here, a series of metal‐insulator‐semiconductor (MIS) junctions, using photoactive n‐type Si (n‐Si) as a light absorber covered by a few‐nanometer‐thick protective SiOx/metal (SiOx/M, with M=Ru, Pt, and Ir) overlayers are investigated for upconversion PECL of the model co‐reactant system involving the simultaneous oxidation of tris(bipyridine)ruthenium(II) and tri‐n‐propylamine. We show that n‐Si/SiOx/Pt and n‐Si/SiOx/Ir exhibit high photovoltages and record stabilities in operation (35 h for n‐Si/SiOx/Ir) for the generation of intense PECL with an anti‐Stokes shift of 218 nm. We also demonstrate that these surfaces can be employed for spatially localized PECL. These unprecedented performances are extremely promising for future applications of PECL. n‐Si/SiOx/Pt and n‐Si/SiOx/Ir exhibit high photovoltages and record stabilities in operation (up to 35 h) for the generation of intense anti‐Stokes photoinduced electrochemiluminescence onto the whole surface of the metal‐insulator‐semiconductor (MIS) photoanode or at a specifically‐chosen location. These results provide solutions for overcoming the instability that has hampered the practical application of upconversion photoinduced electrochemiluminescence (PECL).