After laser-doping with chalcogens, silicon exhibits strong optical absorption at wavelengths corresponding to photon energies less than the band gap. The ab-sorption is connected with the production of mobile electron-hole pairs, even at near-infrared wavelengths. . In the EWT cell, laser drilling is used to make an array of holes in the silicon substrate (Figure 6). A fairly high density of holes (,1 for every 1-2 mm2) is required. . Laser doping in solar cell manufacturing requires precise control of energy delivery, with typical process windows requiring power densities between 1-10 kW/cm² and scan speeds of 10,000-50,000 mm/s. Commercially available transparent spin on dopants were used to obtain surface concentrations higher than 5 x 1019 atoms/cm 3 with junction depths ranging. . ovoltaic cell efficiency enhancement. However, the specific use of lasers for dopant diffusion falls within a broader category of � Laser-Assisted Selective Emitters'.
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