Photoelectrochemical reduction of a Cu(I) complex to copper metal by hot electrons at p-InP

The chemically irreversible reduction of copper(I) (trans-diene)/sup +/ to copper metal has been used to confirm the existence of hot-electron processes at the p-InP/acetonitrile interface. Although hot-carrier processes have been previously reported, this is the first observation of a chemical product produced by a hot-carrier reaction in a photoelectrochemical cell. Band-edge positions have been determined by capacitance measurements done under conditions identical with the hot-carrier copper-plating experiments. Supraband-edge production of Cu(O) occurred at high-doped (1.2 /times/ 10/sup 18/ cm/sup /minus/3/) p-InP but was observed at low-doped (8 /times/ 10/sup 15/ cm/sup /minus/3/) samples. For the high-doped electrode, a quantum yield for production of copper by hot electrons of 0.25% was measured, but this represents only a lower limit to the actual quantum yield for hot electrons since the hot-carrier probe reaction must complete with other processes. Nearly identical quantum yields were measured with both 632.8- and 543.5-nm illumination; however, the intensity profile across the electrode surface has a dramatic effect on the quantum yield.