Screen printed metal contacts to Si solar cells — Formation and synergistic improvements
Silicon solar cell technology has advanced by improvements to all aspects of cell design including metallization. Improvements to metal contacts have been synergistic with other cell improvements such as passivation, lightly doped emitters, and boron doped emitters. This paper briefly recounts the history of c-Si PV metallization technology and its synergy with other cell technologies. It concludes with a perspective on various metal contact mechanisms.
Electron microscopy study of front-side Ag contact in crystalline Si solar cells
Efficiency of industrial screen-printed silicon solar cells depends critically on their firing conditions. We investigated the microstructure of the Ag/emitter contact of solar cells fired at temperatures from below to above optimal by electron microscopy. We found that the interfacial microstructure evolved from one richly decorated with nanometer-size Ag colloids into one with many Ag crystallites grown onto the emitter surface. Selective etching revealed a dearth of Ag crystallites in optimally fired cells. Our microstructural observations suggest that a tunneling mechanism (likely assisted by nano-Ag colloids) is responsible for current extraction in these cells fired with optimal conditions.
Mississippian Barnett Shale: Lithofacies and depositional setting of a deep-water shale-gas succession in the Fort Worth Basin, Texas
The Mississippian Barnett Formation of the Fort Worth Basin is a classic shale-gas system in which the rock is the source, reservoir, and seal. Barnett strata were deposited in a deeper water foreland basin that had poor circulation with the open ocean. For most of the basin's history, bottom waters were euxinic, preserving organic matter and, thus, creating a rich source rock, along with abundant framboidal pyrite. The Barnett interval comprises a variety of facies but is dominated by fine-grained (clay- to silt-size) particles. Three general lithofacies are recognized on the basis of mineralogy, fabric, biota, and texture: (1) laminated siliceous mudstone; (2) laminated argillaceous lime mudstone (marl); and (3) skeletal, argillaceous lime packstone. Each facies contains abundant pyrite and phosphate (apatite), which are especially common at hardgrounds. Carbonate concretions, a product of early diagenesis, are also common. The entire Barnett biota is composed of debris transported to the basin from the shelf or upper oxygenated slope by hemipelagic mud plumes, dilute turbidites, and debris flows. Biogenic sediment was also sourced from the shallower, better oxygenated water column. Barnett deposition is estimated to have occurred over a 25-m.y. period, and despite the variations in sublithofacies, sedimentation style remained remarkably similar throughout this span of time.