Bifunctional Effects of CdSe Quantum Dots and Nb2O5 Interlayer for ZnO Nanorods-based Photoelectrochemical Water-Splitting Cells

• DOI: 10.1016/j.electacta.2014.04.015
• Publication Date: 2014-04-16T03:19:25Z
• Authors: Soon Hyung Kang; Soo-Yong Lee; Myeng Gil Gang; Kwang-Soon Ahn; Jin Hyeok Kim
• Keywords: Nanorod; Passivation; Spin Coating; Deposition

Abstract Single crystalline ZnO nanorods (ZONRs) with a length of 3.6 μm and a diameter of 100 nm were prepared using a hydrothermal method. Based on photoactive ZONR films, the thin Nb 2 O 5 layers were introduced using spin-coating, followed by the deposition of CdSe quantum dots (QDs) as an absorber. The Nb 2 O 5 layers, denoted as Nb 2 O 5 (1) and Nb 2 O 5 (2), were spin-coated one and two times, respectively, to demonstrate the thickness effect of Nb 2 O 5 . The Nb 2 O 5 (1)-coated ZONR (ZONR/Nb 2 O 5 (1)) exhibited a higher photoelectrochemical (PEC) response and better stability than the bare ZONR, due to the surface-related defect states passivated by the Nb 2 O 5 . In contrast, the PEC response of the ZONR/Nb 2 O 5 (2) was reduced about 40% due to the insulating nature of the thicker Nb 2 O 5 . CdSe QD-sensitized ZONR and ZONR/Nb 2 O 5 films were compared, revealing that the ZONR/Nb 2 O 5 (1)/CdSe film exhibited significantly enhanced PEC performance when compared with the other films. Herein, the CdSe QDs acted as the light absorber and, in addition, the QDs on the exposed ZONR passivated the surface-related defect states of the ZONR. The Nb 2 O 5 layers also passivated the surface-related defect states of the ZONR; furthermore, the Nb 2 O 5 located between the ZONR and the QDs led to the stepwise energy band edge alignment, resulting in the faster charge separation. These binfunctional effects contributed to the significantly enhanced PEC response of the ZONR/Nb 2 O 5 (1)/CdSe.