Potentiostatic Elehctro-Deposition of p-n Homo-Junction Cuprous Oxide Solar Cells

A p-n homo-junction copper (I) oxide (cuprous oxide, Cu₂O) solar cell was potentio-statically electro-deposited on an FTO (Fluorine Tin Oxide)-coated glass substrate from a solution containing 0.4M copper (II) sulfate and 3M lactic acid. The deposition was carried out in two stages: in the first stage, n-type cuprous oxide was deposited on the FTO glass substrate using a solution with bath pH of 7.5, and at a constant potential of -0.20V (vs. Ag/AgCl/saturated NaCl) to give a thickness of 16000 Angstrom (1.6μm). While the second stage was characterized with the deposition of a 13000 Angstrom (1.3μm) layer of layer p-type cuprous oxide directly on the already deposited n-cuprous oxide, at a solution pH of 11.56, and applied potential of -0.4V throughout. Bath temperature was maintained at 60°C throughout the deposition processes with continuous stirring. The lactic acid was used to stabilize Cu (II) ions at bath pH higher than 7, while the bath pH was carefully adjusted by the controlled addition of 4M NaOH. The superstrate solar cell configuration has the added advantage of not only serving as a supporting structure, but also as a window for the illumination and as part of the encapsulation. The electrical, structural, and optical characteristics of the cell were well investigated, where values of 0.60mA, 0.453mV, 0.272mW, 0.155mW, 0.336mV, 0.462mA, 0.571 and 0.058% were recorded for the short-circuit current density (J_SC), open-circuit voltage (V_OC), theoretical power (P_Th), maximum power (P_MAX), maximum voltage (V_MAX), and maximum current (I_MAX), fill factor (FF), and efficiency respectively