Understanding the role of Se in defect reduction in CdTe photovoltaics

CdTe devices with CdTe and CdTeSe/CdTe as absorber layer were fabricated. The highest short circuit current density reaches 28.73mA/cm2 of CdTeSe/CdTe device. Besides, defects of devices with different absorber layers were investigated using admittance. A shallow defect with activation energy of 0.09eV was only detected in CdSeTe/CdTe device, which may assign to the hydrogenic defects in CdSeTe alloy. A defect with activation energy of 0.34eV was detected in both devices which might relate to the native impurities. And the defect with activation energy of 0.55eV was only observed in CdTe only devices. Overall, Se is significant to reduce defects in CdTe.