Investigation Of N-Al:Zno/P-Cu2o Heterojunction For C-Si Tandem Heterojunction Solar Cell Applications

In this work, an in-situ growth approach has been employed to fabricate Al:ZnO/Cu2O/Cu and Al:ZnO/ZnO/Cu2O/Cu heterojunctions using direct current (DC) and radio frequency (RF) magnetron sputtering technique in a controlled atmospheric condition. The effect of ZnO buffer layer thickness (30 and 50 nm) as well as in-situ Cu2O annealing at 600 degrees C in low vacuum (similar to 10(-6) Torr) prior to Al:ZnO deposition were studied. The carrier density of Al:ZnO was similar to 2 x 10(20) cm(3) with mobility similar to 8 cm(2)/V.s and resistivity similar to 1 x 10(-3) Omega.cm, while the carrier density of Cu2O was 1 x 10(15) cm(3) with mobility similar to 19 cm(2)/V.s and resistivity similar to 200 Omega.cm. The heterojunctions were investigated by depth resolved Cathodoluminescence (CL) spectroscopy at 80 K to analyze the influence of defects at the interface. The two emissions at 1.51 eV (V-O(+)) and 1.69 eV (V-O(2+)) dominate in all CL spectra related to oxygen vacancy defects in Cu2O. The relative intensity of the defect luminescence band V-O(+) respect to V-O(2+) is greater at the interface compared to bulk Cu2O, while the incorporation of the ZnO layer reduces significantly both radiative recombination and the V-O(2+) related emission at the interface.