Photoelectrochemical Properties of Heterojunction CdTe/TiO₂ Electrodes Constructed Using Highly Ordered TiO₂ Nanotube Arrays

Abstract

A heterojunction CdTe/TiO 2 photoelectrode was prepared by electrochemically filling the tubes and tube-to-tube voids of a TiO 2 nanotube array with CdTe. The TiO 2 nanotube arrays used in this study were prepared by anodizing titanium films, which resulted in closely packed n-type TiO 2 tubes with an average inner pore diameter of 50 nm, wall thickness of approximately 13 nm, and length of 250-300 nm. CdTe was cathodically deposited using TiO 2 nanotubes as the working electrode at E ) -0.4 V vs Ag/AgCl at 85 °C (3H + + Cd 2+ + HTeO 2 + + 6ef CdTe + 2H 2 O). The resulting electrodes contained three-dimensionally organized CdTe/TiO 2 junction structures with significantly enhanced junction areas. Formation of the CdTe/TiO 2 junction improved the photocurrent generation and photostability of the CdTe layer when compared with a two-dimensional CdTe layer deposited directly on a conducting substrate (i.e., fluorine-doped tin oxide). A more intimate and conformal CdTe/TiO 2 junction was formed via a new deposition technique developed in this study that promotes deposition of CdTe only in the TiO 2 tubes while minimizing deposition at the tube entrances, thus preventing pore clogging. The CdTe/TiO 2 electrodes prepared by the new technique created a longer path length for light in the CdTe layer as well as increased CdTe/TiO 2 and CdTe/electrolyte junction areas. This resulted in enhanced photon absorption and photocurrent generation, achieved using a minimal amount of CdTe.

Relation between morphology and conductivity in TiO2 nanotube arrays: an electrochemical impedance spectrometric investigation

“…The outstanding charge transport of TiO 2 nanotubes enables various advanced applications, such as in sensors [5][6][7], dyesensitised solar cells [8][9][10], photocatalysis [11][12][13] and water photo-electrolysis [14][15][16].…”

Sonication-polished anodic TiO2 nanotube array-based photoanode for efficient solar energy conversion

“…Herein, the highest photoconversion efficiency of 6.28 % for the TiO 2 NTAs/Sb 2 S 3 electrode is a fourfold enhancement as compared to that of the bare TiO 2 NRAs sample. To the best of our knowledge, the obtained photoconversion efficiency is one of the top values for anodic TiO 2 NTA-based photoanodes [22,25,26,28]. Besides, the V m (electrode potential at maximum photoconversion efficiency) and V oc (vs SCE) both show negative shifts when loading Sb 2 S 3 into the TiO 2 NTAs, which might be due to retarded interface recombination with the Sb 2 S 3 interlayer.…”

“…In a PEC system, the employed semiconductor nanomaterials usually have multiple functions, such as harvesting photonics, transporting charge carriers, and catalyzing the PEC reactions at interfaces. Recently, TiO 2 nanotube arrays prepared by an electrochemical anodization method (anodic TiO 2 nanotube arrays (NTAs)) have attracted great attentions in the PEC areas [2,[20][21][22][23][24][25][26][27][28], which could be explained by the following reasons. First, this is closely related to the intrinsic features of TiO 2 , such as non-toxicity, low cost, and high stability and flexibility to surface modification.…”

“…Obviously, the poor overlapping with the visible-light spectrum for TiO 2 has greatly limited its application in the PEC fields. As a result, a lot of efforts have been made to induce red shift of the response of TiO 2 to sunlight, such as ion doping [35][36][37][38][39][40][41] and coupling with narrow-bandgap semiconductors [22,[25][26][27][28]42]. Although ion doping could extend light absorption, this method introduced midgap energy levels between the conduction band and valence band of TiO 2 .…”

Metal Chalcogenide Hierarchical Nanostructures for Energy Conversion Devices

“…It can be seen from figure 9.22, effect of some factors on morphology of In fact, for lower deposition potentials no CdS nanowire formation was observed. Seabold and co-workers used TiO 2 as template to grow a CdTe layer by using an electrochemical deposition [47]. Figure 9.23 shows the schematic of this setup and SEM image of the TiO 2 nanotubes with CdTe layer that has been deposited on the TiO 2 nanotubes.…”