Photoluminescence and Electroluminescence in Graded Cadmium Sulfoselenide Electrodes: Applications to Photoelectrochemical Cells

摘要

Inhomogeneous samples of n-type CdS sub X Se sub 1-x (0 < or = X < or = 1) have been prepared by vapor-phase diffusion of S into a single-crystal CdSe substrate. Characterization of the samples by Auger electron spectroscopy (AES)/Ar ion sputter etching reveals that S has substituted for Se in the lattice to produce a graded region: The depth profile analysis indicates that from a composition with X nearly unity at the surface, X monotonically declines to zero over a distance of about 1 micron. Correspondingly, the band gap diminishes from about 2.4 eV for the CdS-like composition to about 1.7 eV for CdSe. Photoluminescence (PL) and electroluminescence (EL) from the graded material appear to derive from the luminescence of the CdS sub X Se sub 1-x compositions which comprise the graded region: emission from about 500-750 nm matches the spectral region spanned by PL and EL from homogeneous, single-crystal CdS sub X Se sub 1-X samples which emit near their band gap energies. A previously established linear correlation between emission maxima (nm) and composition in homogeneous CdS sub X Se sub 1-X samples provides a spatial probe of election hole(e- - h+) pair recombination in the inhomogeneous material: Regions from which PL and EL originate can be inferred from their spectral distribution in combination with the AES/depth profile data.