Structural and spectroscopic studies of CdS/CdTe heterojunction cells fabricated by electrodeposition

CdTe films have been electrodeposited on CdS\SnO2 (F)\glass in a stirred cell and in a channel flow cell. The influence of deposition conditions on recrystallization during annealing treatment has been studied. Films were chararterised by XRD, photocurrent spectroscopy and electroreflectance/absorbance spectroscopy using electrolyte contacts to allow illumination from the CdTe or CdS sides. As-deposited CdTe is generally n-type and tends to show strong preferential [1 1 1] orientation. Thermal treatment in air brings about type conversion. Type conversion is not necessarily accompanied by recrystallization; most of the CdTe films deposited from stirred solution did not recrystallize. Recrystallization did occur for films grown by pulsing the potential periodically from 50 mV to >350 mV vs. Cd2+/Cd during deposition. Tn this case, diffusion of sulfur led to formation of CdTe0.95S0.05. CdTe films were also electrodeposited rapidly in a channel flow cell. Deposition times shorter than 30 min for 2 mu m were achieved. and the films recrystallized fully during thermal annealing. The now cell films produced in this way gave reasonable solar cell performances, holding out the promise of more rapid fabrication of CdS/CdTe cells by electrodeposition. (C) 2000 Published by Elsevier Science S.A. All rights reserved.