Photoelectrochemical properties of cadmium chalcogenide-sensitized textured porous zinc oxide plate electrodes.

We report the photoelectrochemical (PEC) performance of textured porous ZnO and CdX-coated ZnO films (X = S, Se). Porous ZnO films were grown with a platelike morphology on F-doped SnO(2) (FTO) substrates. The growth of ZnO films involves a two-step procedure. In the first step, we electrochemically grew simonkolleite (Zn(5)(OH)(8)Cl(2)·H(2)O) plate films. Annealing of the simonkolleite at 450 °C results in textured porous ZnO films. The as-obtained porous ZnO electrodes were then used in PEC studies. To increase the light-harvesting efficiency, we sensitized these ZnO electrodes with CdS and CdSe quantum dots, using the so-called "successive ion layer adsorption and reaction (SILAR) method". As expected, the photocurrent density systematically increases when going from ZnO to ZnO/CdS to ZnO/CdSe. The highest photocurrent, ∼3.1 mA/cm(2) at 1.2 V vs RHE, was obtained in the CdSe-sensitized ZnO electrodes, because of their enhanced absorption in the visible range. Additionally, quantum efficiency values as high as 90% were achieved with the textured porous ZnO films. These results demonstrate that both CdS and CdSe-sensitized textured porous ZnO electrodes could be potentially useful materials in light-harvesting applications.