Recrystallization in CdTe/CdS

Processing of CdTe/CdS solar cells requires annealing of CdS and CdTr/CdS i n different ambients. It ha?, been proven that the application of a CdCl2 t reatment (or its variant) is important for high efficiency solar cells. Thi s treatment influences the structural and interface properties of the layer s. We have grown CdS layers either by a chemical bath deposition (CBD) or a high vacuum evaporation (HVE) on different transparent conducting oxides ( TCO): tin oxide doped with fluorine (FTO) and indium tin oxide (ITO) coated glass substrates. The CdTe layers have been grown by a HVE method. Effects of the CdCl2 treatment on the recrystallization of CdTe: and CdS have been studied with X-ray diffraction and scanning electron microscopy. An increa se in the grain size of CdTe from about 0.5 to 3-7 mu m, along with the los s of the preferred (111) growth orientation has been observed. The strain a nd recrystallization of CdTe, and intermixing of the CdTe and CdS layers st rongly depend on the deposition and annealing temperatures. An optimum trea tment and a minimum thickness of CBD-CdS is required for high efficiency so lar cells. CdS layers and the method of their deposition also have a strong influence on the microstructure of CdTe and photovoltaic properties. Solar cells with efficiency of 11.2 and 2.5% are obtained with FIVE and CBD grow n CdS window layers. (C) 2000 Elsevier Science S.A. All rights reserved.