N-CuInSe//2 PHOTOELECTROCHEMICAL CELLS: SOLID STATE OR SOLID-LIQUID JUNCTIONS?

The consideration of the title cells as either semiconductor/liquid electrolyte, or as solid-state solar cells is determined by analyzing data from impedance measurements on electrochemical and solid-state devices, and from electron-beam-induced current (EBIC) measurements on the latter. Air oxidation of etched samples leads to an order of magnitude decrease in net donor density near the surface. A small, up to 250 mV, barrier is found without electrolyte contact. Because this barrier is insufficient to account for the observed open current voltage with an electrolyte, and because EBIC shows only part of the interface to be active, it is suggested that the cells still act as semiconductor/liquid electrolyte ones, with air oxidation leading mainly to decreased recombination losses by increasing the depletion layer width. Field-assisted movement of Cu-interstitials or vacancies explains the observed decrease in net donor density.