Photovoltaic cells on CdS/CdTe heterojunctions

Cadmium sulphide and cadmium telluride thin layers are sprayed and electrodeposited, respectively, for n-CdS/p-CdTe solar cells. Approximately equal concentrations of ionized donors and acceptors (4 × 1015 cm−3) in n- and p-parts, respectively, and the thickness of space charge region in CdS which extends over the full width of the CdS film, are derived from the 1/C2–U, specially shaped, dependence. The dark current transport mechanism of the cells is consistent with the tunnelling/interface recombination model. The best photovoltaic parameters deduced from I–U characteristics under illumination equivalent to AM 1.5 are: Jsc = 22 mA/cm2, Uoc = 675 mV, FF = 0.54, η = 7.4%. The spectral response of the short-circuit current agrees well with the generalized theory of the photovoltaic effect published previously. The main contribution to the photocurrent originates from the space charge region in CdTe.