INFLUENCE OF CHLORIDE TREATMENTS ON THE EFFICIENCY OF SOLAR CELLS BASED ON CADMIUM TELLURIDE FILMS OBTAINED BY CLOSE SPACE SUBLIMATION METHOD
In order to increase the efficiency of solar cells (SCs) based on cadmium telluride films obtained by close space sublimation method, various methods of chloride treatment to activate the base layer of solar cells have been investigated. Both gas-phase and solid-state chloride treatment methods were taken to different solar cells, which allowed doing a comparative analysis of the output parameters and light diode characteristics. The effect of annealing time of the CdTe base layer in cadmium chloride vapors during gas-phase chloride treatment was investigated. It is established that the optimal time of this process is about 10 minutes, which provides efficiency increasing to 12.8%. Numerical modeling of the effect of changes in light diode characteristics on the efficiency showed that the increase in the efficiency of SnO2:F/CdS/CdTe SCs is equally due to a series resistance and diode saturation current density decreasing , as well as an shunt resistance increasing. During the solid-state chloride treatment, cadmium chloride layers of various thicknesses were deposited on the cadmium telluride surface, followed by heterosystem annealing in air. It was found that such treatment does not allow the formation of SCs with an efficiency of more than 9%, due to the negative impact of increasing of series resistance and diode saturation current density.
It is established that the effect of chloride treatment on the efficiency is associated with the formation of various defective complexes in the base layer. In the case of gas-phase chloride treatment, small ClTe-VCd acceptors are formed, and in the case of solid-state chloride treatment, isoelectronic 2ClTe-VCd complexes begin to form due to excess chlorine. These complexes affect the light diode parameters of solar cells in different ways, which leads to a significant difference in the SCs efficiency.
Thus, it is established that for SCs with a base layer of cadmium telluride obtained by close space sublimation method, the gas-phase method of chloride treatment is optimal and the optimal physical and technological values of this treatment are determined. Bibl. 10, table. 2, fig. 3.
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