Visible light emission from a porous silicon/solution diode

Reduction of S2O82− ions at the interface between an n-type porous Si electrode and an aqueous solution gives rise to electroluminescence showing evidence of quantization effects. A broad emission band with a maximum at 670 nm is observed similar to the photoluminescence spectrum of the same layers. The results suggest that holes are ‘‘injected’’ into the valence band of the porous semiconductor from an intermediate of the reduction reaction, the SO4−⋅ radical ion. The resulting electron-hole recombination is responsible for the visible light emission.