Optical transmittance properties for CdS films in CdTe-HgCdTe tandem solar cells

Improving the spectral transmittance of CdS window layer used in CdTe-HgCdTe tandem solar cells has a significant impact on the effective utilization of sunlight and increases the device short-circuit current density (J_sc). Herein, the average transmittance (T) and J_sc losses of as-deposited and CdCl₂ annealed CdS films prepared by chemical bath deposition (CBD), near space sublimation (CSS) and magnetron Sputtering (SPUT) are studied. The results show that: in the range of 520-820 nm, the as-deposited and annealed CdS films by CBD exhibit the highest T and the lowest J_sc losses of the CdTe top cell; in the range of 820-1150 and 520-1150 nm, the as-deposited and annealed CdS films by SPUT exhibit the highest T and the lowest J_sc losses of the HgCdTe bottom cell and the CdTe-HgCdTe tandem solar cells. In the range of 520-820, 820-1150 and 520-1150 nm, the CdCl₂ annealing can greatly increase T of CdS films and decrease the J_sc losses of the CdTe top cell, the HgCdTe bottom cell and the CdTe-HgCdTe tandem solar cells.