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 η of 1.06%, a VOC of 0.621 V, an ISC 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.