PHOTOELECTROCHEMICAL BEHAVIOR OF CHEMICALLY DEPOSITED CDSE AND COUPLED CDS CDSE SEMICONDUCTOR-FILMS/

Photoelectrochemical effects at chemically deposited CdSe thin films ( 2000 Angstrom) coupled with as-prepared and air annealed (250 degrees C) CdS films have been investigated by monitoring open-circuit voltage (V-oc) and short-circuit current density (I-sc) at varying incident l ight intensities and for different heat-treatments temperatures. Two c onsecutive chemical baths were used in the coupled system. Each bath h as been optimized in earlier studies for the deposition of highly phot osensitive CdS and CdSe thin films. The photoelectrochemical behavior of single and coupled films was investigated in ferricyanide redox cou ples. The enhanced short-circuit photocurrent of the as-deposited CdS/ CdSe system, despite their lower photosensitivity, indicated that char ge separation improved in the coupled system. The role of post-deposit ion thermal treatments in improving the photoelectrochemical cell char acteristics and stability of coupled semiconductors was investigated. Excellent I-V properties were obtained for CdSe and CdS250/CdSe photoe lectrodes annealed at 280 degrees C. For the coupled system: V-oc = 96 0 mV; I-sc = 8.6 mA/cm(2); fill factor (ff) = 0.53 and cell efficiency (eta) = 4.2%. The linearity of V-oc/ln(I-L) and I-sc/I-L plots suppor ts the Schottky-Mott model for these interfaces. The stability of the coupled photoanode is superior to that of the CdSe only-film for the i nitial 3 h. (C) 1998 Elsevier Science B.V. All rights reserved.