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 SnO2/SnO2:F coated soda-lime glass substrates. With high-temperature close-space sublimation CdTe deposition followed by CdCl2 activation, this thin-film stack allows for substantial interdiffusion at the CdSe/CdTe interface facilitating a CdSexTe1-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 theV(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.