Applications of Surface Science 22/23 (1985) 1075--1082 1075 North-Holland, Amsterdam DERIVATION OF CHARGE TRANSFER PARAMETERS AT SEMICONDUCTOR-LIQUID INTERFACES S. HINCKLEY * and D. HANEMAN School o[ Physics, University of New South Wales, P.O. Box 1, Kensington 2033, Australia Received 27 August 1984; accepted for publication 31 October 1984 The excess-carrier charge transfer velocity, Vcp,is an important parameter describing the efficiency of charge transfer across a solid-liquid interface. By using recent theory to analyze current-voltage curves of photoelectrochemical cells, we have been able to derive values of vcp for CdSe films in aqueous polysulfide electrolytes and measure the effects of varying the sulfur concentration. The parameter, v~, is found to vary at short circuit conditions, from 1.2 × 106 to 1.36 × 106 cm s-1 on increasing the sulfur concentration from 0 to 3.0M. In addition it has been found that v~p has only a weak voltage dependence described by an equation linear in voltage. 1. Introduction The performance of devices like solar cells, which are based on illu- minated semiconductor-liquid interfaces, depends inter alia on successful charge transfer across the interface. However the parameters describing this transfer have only recently been derived from experiment [1,2]. In this paper we describe methodical experiments on CdSe-based photoelectrochemical (PEC) cells in which both the parameters and the form of their dependence on voltage are obtained for different liquid contacts. On of the difficulties in analyzing liquid junctions is that the unknown factors include not only the interfacial recombination and transfer of car- riers, but also recombination in the depletion layer of the semiconductor. Early simplified treatments ignored the latter but it has been shown [3,4] that it plays an important role in practical liquid junctions which incorporate thin films. Such films usually have recombination centres at point defect~ and grain boundaries and cannot approach the quality of single crystal silicon. Theoretical treatments which include the effects of depletion layer recombination and avoid simplifications like fiat quasi Fermi levels have * Now at Telecom Australia Research Laboratories, 770 Blackburn Road, Clayton, Victoria 3168, Australia. 0378-5963/85/$03.30 O Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)