Impact of incorporating sodium into polycrystalline p-type Cu2O for heterojunction solar cell applications

The resistivity was controlled in the range of 10(3) to 10(-2) Omega cm in polycrystalline p-type Cu2O sheets (incorporating sodium (Na)), which are suitable for Cu2O-based heterojunction solar cell applications. The Na-doped Cu2O sheets exhibited a hole concentration that ranged from 10(13) to 10(19) cm(-3). In particular, a hole concentration of 10(13) -10(16) cm(-3) was obtained while maintaining a high Hall mobility above 100 cm(2)/V s, and, in addition, a degenerated semiconductor exhibiting metallic conduction was realized with a hole concentration above about 1 x 10(19) cm(-3). The mechanism associated with the Na doping can be explained by a copper vacancy produced due to charge compensation effects that result when a Na atom is incorporated at an interstitial site in the Cu2O lattice. For solar cell applications, the use of the Cu2O: Na sheet in a heterojunction solar cell successfully improved the obtained efficiency over that found in heterojunction solar cells fabricated using an undoped Cu2O sheet. (C) 2014 AIP Publishing LLC.