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Developing a good back contact material is important for high efficiency CdTe solar cells. In this work, the graphite oxide (GO) was prepared by the Hummers method through liquid oxidization, and the Bi-doping reduced graphene oxides (Bi@RGO) with different concentrations were synthesized by a chemical reduction of GO and BiCl 3 aqueous solution using hydrazine hydrate. The doping concentration of bismuth was varied by controlling the mass ratio of GO/BiCl 3 . The peaks of bismuth and RGO can be easily observed in the X-ray diffraction patterns. Both Raman spectra analysis and infrared spectra analysis also show that RGO is reduced successfully. Transmission electron microscopy shows Bi nanoparticles are entrapped inside the flake-like RGO. Furthermore, Bi-containing RGO/Au system was used as a back contact to CdTe thin film solar cells. The devices with Bi-containing RGO layers were fabricated and their photovoltaic characteristics such as short circuit current density, open circuit voltage, fill factor and efficiency were obtained. The results illustrate that Bi@RGO improves the hole collection ability, and supplies an active Bi diffusion source for the absorption layer, thereby enhancing CdTe solar cell performance. [ABSTRACT FROM AUTHOR]

Phase control is important to obtain high-performance CdTe solar cells when copper telluride is used as a back-contact for CdTe solar cells. In this paper single-phase CuTe was mainly controlled by the Cu/Te ratio via a co-evaporation method in combination with rapid thermal processing treatments. The alloy thin films as-deposited were mainly amorphous. After thermal treatments, the films experienced the phase transformation from mixed phases of CuTe and Cu 1.4 Te to single phase CuTe and then to coexisting phases. Single phase CuTe thin films were p-type semiconductor compounds and had a high carrier concentration, ∼10 21 cm −3 . With the copper telluride buffer layer, device performance than those without the buffer layer has been obtained. Moreover, single-phase orthorhombic CuTe contact buffer layer obviously improved diode characteristics and enhanced the device performance. [ABSTRACT FROM AUTHOR]

Abstract: Bi2Te3 thin films were fabricated by vacuum co-evaporation and the properties of the films were investigated using X-ray diffraction, Hall measurements, and synchrotron radiation photoemission spectroscopy. The results indicate that p-type Bi2Te3 films, which have a work function of about 5.4eV and carrier concentration of the order of 1021 cm−3, are a rhombohedral phase with a strong (105) preferred orientation. A co-evaporated Bi2Te3 buffer layer was used for a back contact to CdTe thin film solar cells. C–V measurements, light and dark J–V measurements, and spectral response analysis also show that the p back contact has greatly enhanced cell performance. [Copyright &y& Elsevier]

Abstract: Vanadium diselenide thin films were prepared by electron beam evaporation. The properties of vanadium diselenide thin films were investigated using X-ray diffraction, scanning electron microscope, transmission spectra, electrical and Hall measurements. To further investigate the application of vanadium diselenide thin films, device performance in CdTe solar cells with a vanadium diselenide layer was also studied. The results indicate that vanadium diselenide thin films had a stable hexagonal structure after annealing. The thin films were p-type semiconductor materials with the high work function and high carrier concentration. Vanadium diselenide thin films could form a good ohmic contact to CdTe solar cells. Thus, cell performance was greatly improved when introduced a vanadium diselenide buffer layer. [Copyright &y& Elsevier]