Nonlinear phenomena in semiconductor photoelectrochemistry

By investigating the photocurrent at the interfaces of different aqueous solutions and of B₆As or tungsten bronzes, it is shown that whereas the kinetics is defined by solid-state processes, i.e. light absorption, charge-carrier transport, and recombination, the magnitude of the current depends on the nature and concentration of charge scavengers dissolved in water. The observed square-root dependence of steady-state photocurrent on light intensity is described in terms of second-order recombination in the solid phase. The effect of the liquid-phase composition proves that atomic hydrogen is the active intermediary at the illuminated interface between tungsten bronze and aqueous solution.