Solution-based n-type doping in Cu2O and its implications for 3rd-generation cells

Cu₂O is naturally p-type, which has prevented an efficient Cu₂O solar cell. N-type doping of Cu₂O is demonstrated during electrodeposition of Cu₂O by adding a Cl precursor to the aqueous solution. Current-voltage characterization reveals that the resistivity of undoped Cu₂O by electrodeposition is ~40 M¿-cm, while that of Cl-doped Cu₂O is significantly reduced to as low as ~7¿-cm. X-ray diffraction confirms that the films are pure Cu₂O. Photocurrent measurements verify that Cl-doped Cu₂O is n-type. The solution-based doping method is particularly suitable for low-cost, large-area and high-throughput fabrication of solar cells. In addition, since the doping method substitutes chalcogen with halogen by co-precipitation of halide with chalcogenide, it is in principle universal for n-type doping in other solution-prepared chalcogenides. Several 3^rd-generation concepts are enabled by the doping method through solution-prepared chalcogenide nanowires, including radial p-n junctions for enhanced charge separation in organic/inorganic hybrid cells and 3-dimensional p-n junctions for decoupling of photon absorption and charge separation in solar cells.