Properties of CdSxTe1-x alloy films [in solar cells]

The authors have performed a comprehensive study of the electrical, optical, structural and vibrational properties of thin films of the ternary alloy CdS_xTe_1-x. 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 Ωcm for CdS-rich films to 1000 MΩcm for CdTe-rich films. X-ray diffraction indicates the films are zincblende below x~0.48 and wurtzite above. Raman 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 provide an improved basis for characterizing the interdiffusion between CdS and CdTe which is critical to high performance in the CdS/CdTe solar cell. Examples of PL from interdiffused layers are given to illustrate applications