Photoelectrochemical Characterization of CdSe Thin Film Anodes

Photoelectrochemical characterization of thin films prepared by a chemical solution growth technique was carried out by linear‐sweep voltammetry, current‐voltage measurements under forward and reverse bias, photocurrent‐wavelength measurements, and electrical impedance measurement techniques. The quality of the present junctions for photovoltaic applications was assessed by examining the effect of varying light intensity on current‐voltage behavior. The ideality factors ( n ) were determined for these junctions by modeling the junction in terms of a Schottky barrier. Values of close to 2 were obtained and were attributed to the dominating influence of recombination‐generation currents (either at the surface or in the depletion region) on the overall photovoltaic characteristics. The presence of a thin, tunnelable layer on the electrode surface was postulated as causing the nonideal current‐voltage behavior particularly in the reverse‐bias regime. Equivalent circuits for the interface were developed using a novel technique for measuring the equivalent parallel conductance and capacitance as a function of signal frequency and applied bias. A method of extracting flatband potentials based on conductance measurements is demonstrated using the thin film/electrolyte interface.