Passivation properties of nitric/phosphoric etching on CdTe films: Influence of the etching time and nitric acid concentration

The chemical etch of CdTe surfaces with a mixture of phosphoric and nitric acids is used in research labs in order to enhance the back-contact formation in CdS/CdTe solar cells. However, the possible passivation effect of this approach has not been studied. In this work we report an investigation about the etching effect of nitric/phosphoric acid mixtures with different etching times (0, 30, 40 and 50 s) and variable concentrations of the nitric acid upon the surface recombination velocity of CdTe films deposited by close space vapor transport. Surface recombination velocities with values as low as 93 cm/s were achieved.