[Show abstract][Hide abstract] ABSTRACT: To make CdTe/CdS solar cells highly efficient, a Cu containing back contact (BC) is generally used. These cells degrade due to Cu diffusion to the front contact which causes shunting; this is shown with secondary ion mass spectroscopy (SIMS) depth profiling. To get a stable but still highly efficient cell, different BC materials and etching treatments were investigated. Chemical etching creates a back surface field (BSF) due to a p+-doped Te-rich CdTe surface. To overcome the naturally existing Schottky barrier between p-CdTe and any metal, a thin buffer layer was evaporated prior to the metallization. Amongst the many investigated BC materials, the most suitable are Sb or Sb2Te3 as a buffer and Mo for metallization. These cells showed high stability under accelerated tests corresponding to 70 years.
Thin Solid Films 05/2001; 387(1-2-387):151-154. DOI:10.1016/S0040-6090(01)00792-1 · 1.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Conventional back contacts on CdTe/CdS solar cells are commonly made with Cu/Au or Cu/graphite. Often the contact limit the solar cells efficiency and the performance degrades because of Cu diffusion to the junction. In order to get stable and "non-rectifying" back contacts Sb has been applied. Pre-depo-sition etching treatments, post-deposition annealing, influence of Sb layer thickness and stability issues have been studied. Different etchants not only clean the surface but they also produce a conducting Te layer on the grain boundaries. Using a mixture of nitric and phosphoric acid and Sb/Au as a back con-tact, 12.5% efficiency cells are obtained. The stability of solar cells depends on the etching solution. Stability tests under continues 1 sun illumination suggest that under optimum condition stable cells with Sb/Au contact can be developed. A comparative analysis of the photovoltaic properties of solar cells with different back contacts will be presented.
Thin Solid Films 02/2000; 361. DOI:10.1016/S0040-6090(99)00842-1 · 1.76 Impact Factor