Abstract
Cadmium telluride (CdTe) thin films of different thicknesses deposited onto titanium dioxide (TiO2) nanoparticle layer by spray pyrolysis deposition (SPD) are demonstrated as major photo-active semiconductor in photo-electrochemical solar cell configuration using iodide/triiodide (I−/I3−) redox couple as a hole transport layer. The CdTe–TiO2 heterogeneous films were characterized by X-ray photoelectron spectroscopy which identified doublet split of Cd 3d and Ti 2p which confirms CdTe and TiO2. Optical absorbance and transmittance of CdTe and TiO2 films which were examined by UV–Vis spectroscopy confirm that the optical bandgap of CdTe is 1.5 eV with a dominant photo-absorption in the spectral window of 350–800 nm, while TiO2 showed a bandgap of 3.1 eV and is optically transparent in the visible spectral window. The present work examined photo-anodes comprising 1, 3, 5, and 10 SPD cycles of CdTe coated on TiO2 nanoparticle layer. The solar cell with 5 SPD cycles of CdTe resulting in 0.4% efficiency. Results can be articulated to the CdTe deposited by 5 SPD cycles provided an optimum surface coverage in the bulk of TiO2, while the higher SPD cycles leads to agglomeration which blocks the porosity of the heterogeneous films.
Highlights
Third generation energy-harvesting technology comprises all thin-film-based solar cells in addition to the excitonic photovoltaic devices which include dye and quantum-dotsensitized solar cells [1,2,3]
The particular sample used for XPS studies utilized 5 cycles of Cadmium telluride (CdTe) on TiO2 which covered the surface completely, and due to the limitation of XPS, the Ti 2p state was not found in the heterogeneous CdTe–TiO2 sample
High-resolution XPS scan was performed on the sample to examine the constituent elements in the heterogeneous film and Fig. 1b shows doublet split of Cd 3d state
Summary
Third generation energy-harvesting technology comprises all thin-film-based solar cells in addition to the excitonic photovoltaic devices which include dye and quantum-dotsensitized solar cells [1,2,3]. Dye- and quantum-dot-based photovoltaic devices are important category in electrochemical solar cell technology due to their high performance and lower cost [4, 5]. Various technical challenges including adsorption and stability of dyes onto electron acceptors, volatile, and corrosive nature of electrolytes are a few major hurdles in the progress roadmap of photo-electrochemical solar cell technology [8, 9]. CdTe is widely used as a major photo-active candidate (bandgap of 1.5 eV) along with CdS as a window layer (bandgap of 2.5 eV) in heterojunction thin-film solar cells [15]. While the other electrochemical solar cells experience major problems in terms of stability and photo-absorption, CdTe thin film can be considered as a highly stable which can be used to harvest photons in the visible spectral energy window.
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