Photoelectrochemical characterization of CdSe thin film anodes

Abstract

Photoelectrochemical characterization of CdSe thin films prepared by achemical solution growth technique was carried out by linear-sweep voltammetry,current-voltage measurements under forward and reverse bias,photocurrent-wavelength measurements, and electrical impedance measurementtechniques. The quality of the present CdSe/electrolyte junctions forphotovoltaic applications was assessed by examining the effect of varyinglight intensity on current-voltage behavior. The ideality factors (n) were determinedfor these junctions by modeling the CdSe/electrolyte junction in termsof a Schottky barrier. Values of n close to 2 were obtained and were attributedto the dominating influence of recombination-generation currents (eitherat the surface or in the depletion region) on the overall photovoltaic characteristics.The presence of a thin, tunnelable CdS layer on the CdSe electrodesurface was postulated as causing the nonideal current-voltage behaviorparticularly in the reverse-bias regime. Equivalent circuits for the CdSe/electrolyte interface were developed using a novel technique for measuringthe equivalent parallel conductance and capacitance as a function ofsignal frequency and applied bias. A method of extracting flatband potentialsbased on conductance measurements is demonstrated using the CdSe thinfilm/electrolyte interface.