Papers by Keyword: Back Contact

Abstract: The large area CdTe thin film samples were used for chloride annealing. The CuCl₂/NH₄Cl solution was attached on the CdTe surface. After annealing treatment, the CdTe solar cells were prepared. The structure of the thin films and the properties of the CdTe solar cells were tested for studying the effect of the ratio of Cu/Cl, solution concentration and the annealing temperature. At last the performance of CuCl₂/NH₄Cl annealing cells, ZnTe back contact cells and C:Te,Cu back contact cells were compared. Without back contact layers the efficiency of the CdTe solar cells reached 11.13% with chloride annealing.

Abstract: To overcome the naturally existing Schottky barrier problem between p-CdTe and any metal, an intermediate semiconductor thin buffer layer is a better choice prior to the final metallization for contact. Among many investigated back contact materials the ZnTe is suitable as a buffer layer. ZnTe thin films were deposited onto glass substrates by the thermal evaporation technique under vacuum ~2×10-5mbar. Undoped ZnTe thin films are highly resistive, extrinsic doping of Cu was made to improve the electrical conductivity. Films were doped by immersing in Cu N_O32.5H2O solutions for Cu doping. To optimize the growth parameters the prepared films were characterized using various techniques. The structural analysis of these films was performed by X-ray diffraction (XRD) technique and optical transmission. X-ray diffraction identified the phases present in these films and also observed that the prepared films were polycrystalline. Also the spectral dependence of absorption coefficient was determined from spectrophotometer. Energy band gap index were calculated from obtained optical measurements data.

Abstract: The peculiarities of photo-electric processes in thin film CdS/CdTe solar cells (SC) with different back electrodes (Cu/Au, ITO, Cu/ITO) have been studied. As it was established by capacitance – voltage (C – V) characteristics, the potential barrier heights for CdTe/Cu/Au and CdTe/ITO were 0.3 eV and 2.2 eV, respectively. The concentrations of charge carriers near back contact consisted 91020 m–3 and 21021 m–3, respectively. A high carrier concentration and high potential barrier of the ITO back contact caused the tunnel – recombination mechanism of the charge transport. The investigations of CdS/CdTe/ITO SC spectral photosensitivity testify a negative impact of the developed grain-boundary surface of the base layer on the processes of diffusion and separation of non-equilibrium current carriers generated by short-wave radiation. It is shown that the deposition of Cu nanolayer before the deposition of ITO films give stable efficiency 10 % for bifacial CdS/CdTe solar cells.

Abstract: Porous silicon (PS) layers were formed by anodization on polished substrates of (1 0 0) Si at different current densities for a fixed anodization time of 30 mins. using different screenprinted/ evaporated back contacts (Ag, Al) respectively. The PS films has been characterized by high resolution X-ray diffraction (HRXRD), photoluminescence (PL), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) techniques respectively. Porosity and thickness of PS layers were estimated by gravimetric analysis. The properties of PS formed using screen-printed Ag & Al as the back contacts (SP-(Ag/Al)) was found to be superior as compared to the corresponding films with evaporated back contacts (EV-(Ag/Al)). The PS formed with screenprinted Ag & Al-back contacts shows better crystalline perfection, higher stability, higher PL efficiency and negligible PL decay compared to that formed with evaporated Ag & Al- as the back contact for the same current density and time of anodization.