Metallization

In this paper, a distributed SPICE-model for a solar cell is worked out. Special attention is paid to the problems of nonhomogeneous current distribution and the effective series resistance. Elaborate experimental techniques have been used to determine the model parameters. They are based on the I-V characteristics, the small signal impedance, and the open-circuit voltage decay measurements. The SPICE simulation results are compared with the measured static and dynamic characteristics of a solar cell. We found satisfactory agreement concerning the static characteristics* whereas there is discrepancy in the dynamic characteristics. This is because the SPICE-model of a p -n junction diode contains only one time constant. It is found that two time constants are necessary for accurate description of the dynamic performance. The techniques and methodologies developed here are applicable to other junction diodes operating at high frequencies or under transient conditions.

In this paper the fabrication of conductive aluminum paths on AlN ceramic's surface due to the interaction of laser radiation Nd:YAG (1.064 m) is presented. The metallization process produces an appropriate power value on the ceramics surface to ensure the correct temperature (2200 • C) for which aluminum and nitrogen bonds are broken. Studies have been undertaken on creating low-ohmic structures depending on the parameters such as radiation power, scanning speed, the coverage of subsequent pulses and the environmental impact of the process (air, nitrogen, argon). Furthermore, with regards to the application of this method, it was significant to determine the thickness of the functional layer. A structure of the resistivity of = 0.64 × 10 −6 m and aluminum layer thickness of 10 m was achieved for the process carried out on the inert gas, argon. In addition, a quantitative analysis of nitrogen and aluminum for lasertreated structures was conducted. The performed tests confirmed that the highest amount of aluminum was produced on the surface treated by laser radiation in the environment of the process gas, argon.

Cobalt metallic films are the subject of an ever-expanding academic and industrial interest for incorporation into a multitude of new technological applications. This report reviews the state-of-the art chemistry and deposition techniques for cobalt thin films, highlighting innovations in cobalt metal-organic chemical vapor deposition (MOCVD), plasma and thermal atomic layer deposition (ALD), as well as pulsed MOCVD technologies, and focusing on cobalt source precursors, thin and ultrathin film growth processes, and the resulting effects on film composition, resistivity and other pertinent properties.

The formation of a porous layer on the surface of gallium arsenide anode, n-GaAs, increases photogenerated currents significantly. This layer was formed as a result of an anodic polarization of illuminated n-GaAs in acidified chloride electrolytes. The formation of the porous layer was confirmed by scanning electron microscopy micrographs. The porous layer increases the reflectivity of GaAs to light, thus enhances the photogenerated current density. In addition, the formation of the porous layer enriches GaAs surface with arsenic. As a result of this enrichment, the positions of the energy levels on the semiconductor surface might have been changed in favor of oxidizing the electrolyte rather than consuming electron-hole pairs in recombination processes within surface states. The n-GaAs with porous surface layer was employed as the working electrode in a photoelectrochemical cell with dimethylviologen as a reversible electrolyte. The rates of the anodic reaction, at GaAs, and cathodic reaction, at a Pt counter electrode, are about equal, only when the surface area of the Pt counter electrode is approximately 20 times greater than that of the n-GaAs. Equal rates of reduction and oxidation of the dimethlviologen redox couples reveals that the number of the photogenerated electrons and holes getting into the electrolyte are the same. Therefore, the photogenerated holes formed at GaAs surface are consumed totally as a result of the electrolyte oxidation rather than GaAs corrosion. The deposition of a thin layer of gold on the top of the porous surface doubles the magnitude of the photocurrent density due to suppressing electron-hole recombination process. ᮊ

This letter reports on an innovative front grid design that is capable of: 1) decreasing the metal shading; 2) increasing the short-circuit current (J SC); 3) increasing the open-circuit voltage (V OC); 4) maintaining the fill factor; and 5) increasing the efficiency of an industrial Al back surface field (Al-BSF) solar cell. Because the design incorporates four-streets and five-busbars (4S-5BB), it uses less front silver metal (∼73 mg) than the conventional 3BB (∼129 mg), hence the cost reduction from 6.07 to 3.426 ¢ per cell in metallization with no additional processing step. The 4S-5BB design has shown great potential for achieving >20% efficiency for the industrial size Al-BSF silicon solar cell. In this letter, the preliminary result for the 4S-5BB industrial Al-BSF cell having average efficiency of 19.66% compared with 19.3% 3BB counterpart is presented.

In this paper lead-free silver ink for the front side metallization of silicon solar cells is investigated. Lead is replaced by bismuth. The etching of the silicon nitride anti-reflection coating and the crystallite formation is studied by varying the amount of bismuth oxide added to the ink. Bismuth oxide was either incorporated into the glass frit or added as a powder. The results are compared to our standard lead based standard ink. All inks were applied with aerosol jet printing. For characterization SEM imaging, contact resistance measurements, and the current-voltage-characteristics of the prepared solar cells are used. Concerning the solar cell efficiency, it is found that bismuth glass inks provide a similar efficiency in comparison to the lead based ink.