Abstract

ABSTRACTIntermixing at the CdS/CdTe interface is considered crucial for the performance of CdTe-based solar cells. High-efficiency devices have been fabricated in spite of large lattice mismatch between CdS and CdTe. Intermixing and formation of CdSxTe1−x alloys in present-generation devices result from high-temperature CdTe deposition and post-deposition CdCl2 treatment. In this paper, we present our work on preparation of CdSxTe1−x-alloy powders and films. In this process, the CdS and CdTe powders are sized and mixed, isostatically pressed into a bar, sealed into closed-quartz ampoules, annealed at temperatures >1000°C, and water quenched. X-ray diffraction (XRD) analysis showed that they contained only distinct phases on S-rich and Te-rich sides of the phase diagram. Recently, two new batches of CdSxTe1−x material, produced by an improved process have been obtained (x =0.71 and x= 0.35 in CdSxTe1−x alloy). Initial XRD results from the films deposited by close spaced sublimation (CSS) using these powders reveal that both samples of bulk powders (prior to CSS deposition) are single-phase and demonstrate CdS-like characteristics (hexagonal). We have deposited CdSxTe1−x-alloy films using these powders. These alloy powders evaporate more congruently as opposed to mixed powders of CdS and CdTe. We will also present results on the structural properties of thin CdSxTe1−x alloy films deposited using these powders by CSS.

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