Cl-doping effect in ZnTe_1-xO_x highly mismatched alloys for intermediate band solar cells

Cl doping in highly mismatched ZnTe_1-xO_x (ZnTeO) alloys was achieved by molecular beam epitaxy using ZnCl₂ as a dopant source. The temperature dependence of the bandgap energies for both upper and lower subbands, E₊ and E₋, of ZnTeO was determined by photoreflectance, and it was found to vary in accordance with those expected by the band anticrossing model. Secondary ion mass spectroscopy indicates that the Cl concentration increases with increasing ZnCl₂ cell temperature. Low temperature photoluminescence (PL) spectra show the broad PL peak near the E₋ band. Intermediate band solar cells (IBSCs) fabricated using ZnTeO:Cl exhibit improved short circuit current and open circuit voltage. The results suggest that the Cl doping can effectively improve the PV properties of ZnTeO-based IBSCs and, therefore, is potentially useful for the realization of high efficiency IBSCs.