Single-crystal p–i–n-Si thin-film solar cells grown on Si substrate by sputter epitaxy

Abstract

An intrinsic sputter-epitaxial (SE) Si film with a thickness of 1000 nm and a 50-nm-thick n+ SE-Si film were successfully grown as the light-absorbing layer and emitter layer, respectively, on a heavily doped p-Si(100) wafer to form the p–i–n junction of a solar cell (SC). Heavily doped n+ SE-Si with an electron concentration n of 3 × 1020 cm−3 was grown by cosputtering of Sb with Si. The characteristics of SE-Si grown at 310 °C was investigated in relation to annealing temperature. The oxygen concentration in SE-Si was ∼1018 cm−3, which was found to originate from the gas released in the chamber. Oxygen-induced thermal donors then became the source of n in the film, and n was reduced to 1 × 1016 cm−3 after forming-gas annealing at 700 °C because the thermal donors were neutralized by hydrogen. The SC exhibited a maximum internal quantum efficiency of 73.7%.

Bottom gate single crystal Si thin-film transistors fabricated by all sputtering processes

“…The ρ of our p-doped c-Si strip was comparable to that of the laser doping using excimer laser and the CVD 5 nm P film as the dopant source (5 × 10 −4 Ωcm), 26,27) and superior than that of the laser doping using excimer laser and H 3 PO 4 solution as the dopant source (∼1 × 10 −1 Ωcm). 28) The reason for the much lower ρ in Sb laser doping is the nonvolatile Sb compared to volatile The ρ of the Sb-doped c-Si strip was only slightly higher than that of our sputter epitaxial n + -Si on Si(001) of 7 × 10 −4 Ωcm using the same target composition, 29,30) The Hall electron density and mobility of epitaxial n + -Si were 3 × 10 20 cm −3 and 30 cm 2 V −1 s −1 , respectively. This result indicates that laser doping using Sb dopants is a promising method for realizing heavily doped n + c-Si strips.…”

Direct Current Sputter Epitaxy of Heavily Doped p+ Layer for Monocrystalline Si Solar Cells

“…The cathode power was kept at 100 W over this study. Details on sputter epitaxy can be further referred to in our previous studies [8,9]. p + n monocrystalline Si SCs were fabricated, together with n + p monocrystalline Si SCs for comparison.…”

“…Thus alternative method for formation of shallow and heavily doped n + and p + region under low thermal budget was demanded. To address this problem, we have proposed applying sputter epitaxy for n + emitter for SCs [8,9]. This is a low-temperature process-so forgoing dopants did not diffuse during subsequent opposite dopant type region formation-and also is a low-pressure process, so shadow-mask patterning with a minimum line and space width of ∼0.08 mm can be realized [10].…”

“…This is a low-temperature process-so forgoing dopants did not diffuse during subsequent opposite dopant type region formation-and also is a low-pressure process, so shadow-mask patterning with a minimum line and space width of ∼0.08 mm can be realized [10]. In our previous study, Sb was cosputtered with Si to grow n + -Si on Si substrate, and an abrupt dopant profile with a maximum Hall carrier concentration at 3 × 10 20 cm −3 was obtained [9]. Furthermore, n + emitter was grown on p-Si to form n + p SCs and had demonstrated that internal quantum efficiency (IQE) of the SCs around visible light can be as high as 95%, even higher than that in SCs with conventional thermal diffusion emitter [8].…”