Crystalline Si solar cells fabricated by CO2 laser doping
We proposed CO<sub>2</sub> laser doping technique as a fabrication method of c-Si solar cell, and demonstrated its availabilities with the cell characteristics. P and B-doping with relatively high carrier density around 10<sup>20</sup> cm<sup>-3</sup> were realized by the CO<sub>2</sub> laser irradiation. We found that the pulse frequency is one of the most important parameter to improve the cell performances.
Laser-Doping Technique Using Ultraviolet Laser for Shallow Doping in Crystalline Silicon Solar Cell Fabrication
The laser-doping technique in silicon solar cell fabrication is now attracting considerable attention because of its suitability for the low-cost processing of high-efficiency silicon solar cells; it can be performed at room temperature in air and intricate doping areas can be formed easily. In this study, we used a laser with a UV wavelength (355 nm) instead of the conventionally used laser with 532 nm wavelength to form property-controlled doping regions for the emitter or back surface field (BSF) of silicon solar cells at room temperature in air. The doping depth of phosphorus or boron was precisely controlled in the shallow region under 0.3 µm depth by changing the laser output power, remaining a high doping concentration at the silicon surface. The photovoltaic performance depended strongly on the doping conditions, and the best cell with a laser-doped emitter showed almost the same open circuit voltage and short circuit current as those of a cell fabricated by the conventional thermal diffusion method. In addition, all photovoltaic properties were enhanced by the formation of a laser-doped BSF layer. The problem of a lower fill factor still remained because of the high sheet resistance caused by laser damage, inhomogeneous doping, or the unintentional incorporation of oxygen and/or carbon atoms. However, the utility of the laser-doping technique was clearly shown; silicon solar cells were fabricated below 100 °C.
Geomagnetic Polarity Epochs: Sierra Nevada Data, 3
Available paleomagnetic and radiometric results for about 60 igneous rocks 3.6 m.y. old or less are consistent with the following geomagnetic polarity epoch time scale: Brunhes normal polarity epoch, 0.0 to 0.85±0.15 million years; Matuyama reversed polarity epoch, 0.85±0.15 to 2.4±0.1 million years; Gauss normal polarity epoch, 2.4±0.1 to 3.35±0.1 million years; Gilbert reversed polarity epoch, 3.35±0.1 million years to (?). A brief interval of normal polarity (the Olduvai event) occurs within the Matuyama reversed epoch at about 1.9 m.y., and a brief interval of reversed polarity (the Mammoth event) occurs within the Gauss normal epoch at about 3.06 m.y. Data for twelve units from eastern California and Nevada, reported here for the first time, are particularly useful in defining the Gauss-Gilbert boundary and for recognizing the Mammoth event.