Electrochemical synthesis of cu-doped znte films as back contacts to cdte solar cells

Electrochemical deposition of Cu-doped ZnTe films was investigated as a back contact material for CdTe solar cells. The deposition system consisted of a potentiostat, a substrate (cathode), a Pt counter electrode, and an Ag/AgCl reference electrode. Experimental conditions were pH=2.5∽4, deposition temperature=70 ∽80°C, electrolyte concentration=0.02 M Zn2, 10-4 M TeO2, and deposition potential (Va) = -0.85 ∽ -1.0 V vs Ag/AgCl A cyclic voltammogram obtained from an ITO substrate showed a ZnTe reduction peak at Va = -0 7 ∽ -0 9 V A film obtained at pH=2.5, Va=-0.975 V showed the strongest ZnTe X-ray diffraction peak, but its surface morphology was not as smooth as the films made under the condition of pH=3∽4, Va=-0.950V. Triethanolamine did not form a complex with cu2 in acidic solution as needed for uniform Cu-doping, but oxalate anion and 1,10-phenanthrolme did at pH=2∽3. The efficiency of CdTe solar cells increased from 3.4% to 7.1% when Cu-doped ZnTe film was used as the back contact.