**5. Processing of Cu(In,Ga)Se2 and CdTe thin films into solar cells**

Cu(In,Ga)Se2 and CdTe PV devices are obtained by forming p-n heterojunctions with thin films of CdS. In this type of structure, n-type CdS, which has a band gap of 2.4 eV, not only forms the p-n junction with p-type CuInSe2 or p-type CdTe but also serves as a window layer that lets light through with relatively small absorption. Also, because the carrier density in CdS is much larger than in CuInSe2 or CdTe, the depletion field is entirely in the absorber film where electron-hole pairs are generated (Birkmire and Eser, 1997). After solar cell completion the photovoltaic parameters like Isc, Voc, FF and conversion efficiency were tested by doing the I-V characterization for the two structures; CdTe and Cu(In,Ga)Se2. All the parameters were measured under AM1.5 illumination.
