Li-doped Cu2O/ZnO heterojunction for flexible and semi-transparent piezoelectric nanogenerators

Abstract We have investigated the characteristics of p-type Li-doped Cu 2 O (LCO) films grown by radio frequency magnetron sputtering to use as p-n heterojunction for flexible and semi-transparent piezoelectric nanogenerators (PENGs). Electrical, optical, morphological properties of the LCO films were examined as a function of Ar/O 2 flow ratio as well as work function. The LCO films grown at Ar/O 2 ratio of 20/4 sccm film showed a p-type behavior with resistivity of 2.12 Ω-cm, mobility of 0.364 cm 2 /V-s, and carrier concentration of 8.07×10 19  cm -3 . To overcome the piezoelectric potential screening effect of conventional ZnO-based PENGs, the p-type LCO layer was employed. Due to the enhanced piezoelectric potential coupled with the reduced total capacitance, the PENG with a p-LCO/n-ZnO heterojunction demonstrates the much higher output power up to ~52 μW than PENG only with ZnO layer (7 μW). The improved output power of PENGs indicates that sputtering of the p-type LCO layer on the n-type ZnO is the effective method to overcome the limit of the ZnO-based PENGs.