Celdas solares de heterounión de CdS/CdTe. Parte 2. Celdas solares procesadas por las técnicas de erosión catódica magneto-planar y GREG

We present the processing and characterization of CdS/CdTe thin film solar cells depositing CdS by rf planar-magnetron sputtering and CdTe by the gradient recrystallization and growth, GREG technique. CdS was deposited on soda-lime LOF^™ conducting glass substrates, then CdTe on CdS and Cu-Au contacts evaporated on the CdTe film. The films deposition parameters were: for CdS a 25 W rf power was used at 18 mtorr of Ar pressure and a substrate temperature T_S of 380°C, while for CdTe a source temperature T_f between 570°C and 650°C and T_S from 460°C to 480°C were used under a 500 mtorr Ar pressure. CdS and CdTe films were polycrystalline showing preferential orientation in the (002) direction for CdS and in the (111) direction for CdTe; grain size was 0.1 μm for CdS and 0.5-2 μm for CdTe. The photovoltaic parameters were determined yielding the best solar cell performance values of V_OC = 0.74 V, I_SC = 2.3 mA, ff = 55%, SQE_max = 0.7 electrons/photon at 600 nm and 8% solar energy conversion efficiency.