Properties of CdS/sub x/Te/sub 1-x/ alloy films [in solar cells]

Abstract

0.031 0.01 7We have performed a comprehensive study of the electrical, optical, structural, and vibrational properties of thin films of the ternary alloy CdSxTel.,. The films were grown using pulsed laser deposition (PLD) from pressed targets of the binary alloys. Hall and conductivity measurements have been performed on these films yielding resistivities from 0.5 R-cm for CdS-rich films to 1000 MR-cm for CdTe-rich films. X-ray diffraction indicates the films are zincblende below x -0.48 and wurtzite above. Rarrian scattering shows that the phonon dynamics have two-mode behavior. The x-dependence of the Raman data is described well by a modified random element iso-displacement model. Photoluminescence (PL) is particularly useful in the regions of low and high x-values. These data proviide an improved basis for characterizing the interdiffusion lbetween CdS and CdTe which is critical to high performance in the CdS/CdTe solar cell. Examples of PL from interdiffiused layers are given to illustrate applications.

High-Efficiency Thin-Film Cadmium Telluride Photovoltaic Cells; Final Subcontract Report, Final Technical Report, 21 January 1994-31 March 1998

“…Hence, α is zero if no clustering occurs at all (random distribution of S and Te), and equals one for a completely phase-separated material. We expect that the anions in alloys near the end points of the compositional range i.e., CdTe with trace amounts of S (x≈0 ) and CdS with trace amounts of Te (x≈1), will be arranged in random fashion [2][3][4][5][6][7][8][9][10][11] and that alloys at the midrange of the miscibility gap will undergo incipient phase separation (clustering) to the greatest extent. We assume that α is an analytic function of x which goes to zero at x=0 and x=1 and is at a maximum at x=0.5.…”

Characterization of CdSxTe1-xthin films through thermoelectric power measurements

“…Interdiffusion between the window and absorber layer materials occurring during the fabrication of CdS/CdTe solar cells has been widely reported [1][2][3][4]. Some interdiffusion seems necessary for a high-efficiency solar cell, but excessive interdiffusion leads to a worsening of the device performance [5]. The interdiffusion processes can be reduced by depositing a CdS x Te 1−x absorber layer having S content near the solubility limit [6,7].…”