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 CdCl2activation, this thin-film stack allows for substantial interdiffusion at the CdSe/CdTe interface facilitating a CdSexTe1-xalloy 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 (VOC). To overcome the VOCloss and maintain a high short-circuit current (JSC), 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 VOCimprovement. With an optimized synthesis process, a small-area cell using CdS:O/CdSe window layer showed an efficiency of 15.2% with a VOCof 831 mV, a JSCof 26.3 mA/cm2, 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.