Development of efficient and stable back contacts on CdTe/CdS solar cells

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 fro nt contact which causes shunting; this is shown with secondary ion mass spe ctroscopy (SIMS) depth profiling. To get a stable but still highly efficien t cell, different BC materials and etching treatments were investigated. Ch emical etching creates a back surface field (BSF) due to a p(+)-doped Te-ri ch CdTe surface. To overcome the naturally existing Schottky barrier betwee n p-CdTe and any metal, a thin buffer layer was evaporated prior to the met allization. Amongst the many investigated BC materials, the most suitable a re Sb or Sb2Te3 as a buffer and Mo for metallization. These eels showed hig h stability under accelerated tests corresponding to 70 years. (C) 2001 Pub lished by Elsevier Science B.V. All rights reserved.