Processing of CdTe/CdS solar cells requires annealing of CdS and CdTe/CdS in different ambients. It has been proven that the application of a CdCl2 treatment (or its variant) is important for high ef®ciency solar cells. This treatment infuences the structural and interface properties of the layers. 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 increase in the grain size of CdTe from about 0.5 to 3±7 mm, along with the loss of the preferred (111) growth orientation has been observed. The strain and recrystallization of CdTe, and intermixing of the CdTe and CdS layers strongly depend on the deposition and annealing temperatures. An optimum treatment and a minimum thickness of CBD±CdS is required for high ef®ciency solar cells. CdS layers and the method of their deposition also have a strong infuence on the microstructure of CdTe and photovoltaic properties. Solar cells with ef®ciency of 11.2 and 2.5% are obtained with HVE and CBD grown CdS window layers.
Recrystallization in CdTe/CdS
ROMEO, Alessandro;
2000-01-01
Abstract
Processing of CdTe/CdS solar cells requires annealing of CdS and CdTe/CdS in different ambients. It has been proven that the application of a CdCl2 treatment (or its variant) is important for high ef®ciency solar cells. This treatment infuences the structural and interface properties of the layers. 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 increase in the grain size of CdTe from about 0.5 to 3±7 mm, along with the loss of the preferred (111) growth orientation has been observed. The strain and recrystallization of CdTe, and intermixing of the CdTe and CdS layers strongly depend on the deposition and annealing temperatures. An optimum treatment and a minimum thickness of CBD±CdS is required for high ef®ciency solar cells. CdS layers and the method of their deposition also have a strong infuence on the microstructure of CdTe and photovoltaic properties. Solar cells with ef®ciency of 11.2 and 2.5% are obtained with HVE and CBD grown CdS window layers.
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