Current Enhancement of CdTe-Based Solar Cells

We report on the realization of CdTe solar cell photocurrent enhancement using an n-type CdSe heterojunction partner sputtered on commercial SnO
₂
/SnO
₂
:F coated soda-lime glass substrates. With high-temperature close-space sublimation CdTe deposition followed by CdCl
₂
activation, this thin-film stack allows for substantial interdiffusion at the CdSe/CdTe interface facilitating a CdSe
_x
Te
_1-x
alloy formation. The bowing effect causes a reduced optical bandgap of the alloyed absorber layer and, therefore, leads to current enhancement in the long-wavelength region and a decrease in open-circuit voltage (V
_OC
). To overcome the V
_OC
loss and maintain a high short-circuit current (J
_SC
), the CdTe cell configuration has been modified using combined CdS:O/CdSe window layers. The new device structure has demonstrated enhanced collection from both short-and long-wavelength regions as well as a V
_OC
improvement. With an optimized synthesis process, a small-area cell using CdS:O/CdSe window layer showed an efficiency of 15.2% with a V
_OC
of 831 mV, a J
_SC
of 26.3 mA/cm
²
, and a fill factor of 69.5%, measured under an AM1.5 illumination without antireflection coating. The results provide new directions for further improvement of CdTe-based solar cells.