A photoelectrochemical study of p-n heterojunction between P3HT and nanodendrite CdTe sensitized ZnO nanotube array

Abstract

In this paper, we fabricated a semiconductor-sensitized solar cell using the photoelectrode based on poly(3-hexylthiophene) (P3HT) modified nanodendrite CdTe coated ZnO nanotube array (P3HT@CdTe@ZnO) composite film. One-dimensional vertically ordered ZnO nanotube arrays were prepared on ITO conductive glass substrate by electrochemical etching of the electrodeposited ZnO nanorod arrays in alkaline solution. Nanodendrite CdTe was electrodeposited on ZnO nanotube array, and a CdTe nanodendrite coated ZnO nanotube array shell-core structure was obtained. Different CdTe nanodendrite length could be obtained by adjusting the total charge quantity applied during deposition. Then a thin P3HT layer was spin-coated onto the above nanostructure, and a P3HT@CdTe@ZnO composite film was obtained. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive-ray spectroscopy (EDS) were used to characterize the samples. The photoelectrochemical properties of the above samples were studied, and the results showed that CdTe and P3HT were excellent n-type and p-type materials. A suitable length of CdTe nanodendrite could improve the photovoltaic properties of the solar cell, which was attributed to the enhanced light absorption in the visible region and the decrease in the recombination of photogenerated electrons and holes due to the multiple channels provided by nanodendrites. It has been demonstrated that the favourable hole transportation material P3HT coated on the surface of the CdTe@ZnO shell-core nanotube array largely improved the photoelectrochemical performance. A heterojunction was formed in the interface between n-type CdTe and p-type P3HT, and played an important role in the efficient charge separation and fast charge transportation. A semiconductor-sensitized solar cell with the P3HT@CdTe@ZnO film as photoactive layer was fabricated. The photovoltaic properties of the semiconductor-sensitized solar cell was studied, and the mechanism of the solar cell was investigated. An energy conversion efficiency up to 1.38% with short circuit current density (Jsc) 8.980 mA/cm2, open circuit voltage (Voc) 0.599 V, fill factor (FF) 0.26 respectively was obtained with the designed semiconductor-sensitized solar cell. © 2014 Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.