Secondary Ion Mass Spectrometry Studies of Polycrystalline Thin-Film Cdte/Cds Solar Cells

Polycrystalline thin films of CdTe deposited on CdS are one of the most promising materials systems currently being investigated for the fabrication of low cost, large area, high efficiency photovoltaic devices. However, many of the deposition processes being used to fabricate these thin film materials have not yet been well characterized. It has been found that a post-fabrication heat-treatment is necessary to improve the quantum efficiency of these devices. Secondary ion mass spectrometry (SIMS) was used to study the interdiffusion of S and Te in CdTe/CdS structures grown by two different methods. The depth profiles revealed significant differences in the sputtering behavior depending on the film morphology.Two sets of CdTe/CdS samples were studied. The first set of films was deposited at high temperature using a spray pyrolysis technique with no post deposition anneal. The second set of films was electroplated, followed by treatment with CdCl2 and a high temperature anneal.