Junction studies on electrochemically fabricated p-n Cu2O homojunction solar cells for efficiency enhancement

p-n Cu2O homojunction solar cells were electrochemically fabricated by consecutively depositing an n-Cu2O layer on a p-Cu2O layer. In order to better understand the Fermi levels of the electrochemically grown polycrystalline p-and n-Cu2O layers and maximize the overall cell performance, the back and front contacts of the Cu2O homojunction cells were systematically changed and the I-V characteristics of the resulting cells were examined. The result shows that the intrinsic doping levels of the electrochemically prepared p-Cu2O and n-Cu2O layers are very low and they made almost Ohmic junctions with Cu metal with which previously studied p-Cu2O layers prepared by thermal oxidation of Cu foils are known to form Schottky junctions. The best cell performance (an eta of 1.06%, a V-OC of 0.621 V, an I-SC of 4.07 mA cm(-2), and a fill factor (ff) of 42%) was obtained when the p-Cu2O layer was deposited on a commercially available ITO substrate as the back contact and a sputter deposited ITO layer was used as the front contact on the n-Cu2O layer. The unique features of the p-n Cu2O homojunction solar cell are discussed in comparison with other Cu2O-based heterojunction solar cells.