A simple Sb2Te3 back-contact process for CdTe solar cells

CdTe solar technology has proved to be a cost-efficient solution for energy production. Formation of the back contact is an important and critical step in preparing high-efficiency, stable CdTe solar cells. In this paper we report a simple CdTe solar cell (Sb<inf>2</inf>Te<inf>3</inf>) back contact-formation process. The CdS and CdTe layers were deposited by close-space sublimation. After CdCl<inf>2</inf> annealing treatment, the CdTe surface was etched by use of a mixture of nitric and phosphoric acids to obtain a Te-rich surface. Elemental Sb was sputtered on the etched surface and successive post-annealing treatment induced Sb<inf>2</inf>Te<inf>3</inf> alloy formation. Structural characterization by x-ray diffraction analysis confirmed formation of the Sb<inf>2</inf>Te<inf>3</inf> phase. The performance of solar cells with nanoalloyed Sb<inf>2</inf>Te<inf>3</inf> back contacts was comparable with that of reference solar cells prepared with sputtered Sb<inf>2</inf>Te< inf>3</inf> back contact from a compound sputter target.