Structural, Morphological and Raman Studies of CdS/CdSe Sensitized TiO2 Nanocrystalline Thin Films for Quantum Dot Sensitized Solar Cell Applications

Abstract

Background: It is well known that quantum dot-sensitized solar cells based on nanostructured semiconductor films are considered as a promising alternative to silicon-based solar cells. The aim of this paper is to investigate the structural and morphological properties of CdS/CdSe quantum dot sensitized photoanodes based on nanocrystalline TiO2 thin films considering their performance can reach an efficiency of 2.7%. Methods: TiO2 thin films were prepared on fluorine tin oxide (FTO) glass via the chemical route using commercial Degussa 25 and crystallized at 550°C. Furthermore, a layer of CdS and CdSe nanoparticles was deposited on the titania film by a sequence of successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) methods. After preparation, samples were analyzed using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy for their structural properties and composition. Scanning electron microscopy (SEM) was used to investigate their surface morphology, while energy dispersive X-ray spectrometry (EDS) was used to analyze the sample stoichiometry. Results: The structural properties and morphology of quantum dot sensitized photoanodes revealed that the titania thin films were highly crystalline belonging predominantly in the tetragonalanatase structure, while the CdS/CdS quantum dots were in the cubic phase. Furthermore, scanning electron microscopy (SEM) along with energy dispersive X-Ray mapping EDS showed little contamination. Conclusions: Combined analysis suggests that our preparation route leads to highly crystalline, stoichiometric photoanodes. This plays an important role in the performance of the quantum dot sensitized solar cells.