ZnO-ZnTe nanocone heterojunctions for efficient carrier transport for photovoltaic conversion

Vertically aligned ZnO nanocones were synthesized as cores by utilizing the growth rate difference between terrace and edge sites of nucleation domain during thermal vapor deposition. The p-n junctions were formed by subsequent growth of ZnTe as shells on the nanocone surface using PLD. The polycrystalline structures were observed for ZnTe shells, while the wurzite structure was shown for ZnO cores. Typical I-V characteristics of p-n junction were obtained for the nanocone core-shell structure, but not for the nanorod structure. These structural and electric characteristics indicate that ZnO nanocones are more feasible than ZnO nanorods as practical heterojunctions because the sloping facets of the nanocones facilitate deposition of ZnTe by PLD without the deleterious effects of shadowing. Furthermore, based on theoretical modeling of nanostructure heterojunctions, the nanocone-based junction exhibits an electrostatic potential profile that is much more effective for carrier transport than the electrostatic potential for the nanorod-based junction.