Production of thin (70-100 μm) crystalline silicon cells for conformable modules

N-type multicrystalline silicon wafers and rear junction solar cells

“…Figure 7 shows that the conversion efficiency does not change significantly when S is below 10 3 cm/s. We have verified that values of S lower than 100 cm/s are obtained after a front surface phosphorus diffusion at 850 • C for 20 min and that acceptable p + n junctions are obtained after annealing of the Al-Si structures at temperatures in the range 850 to 900 • C. The diffusion potential is around 0.8 eV and recombination and diffusion density currents are about 10 −6 A/cm 2 and 10 −8 A/cm 2 , respectively, in agreement with the results of Ebarra group [9,10] The photovoltaic parameters of 4 cm 2 RJC cells made with a 300 µm thick raw wafer and an evaporated aluminium layer are: V oc ∼ 560 mV and J sc ∼ 16 mA/cm 2 without antireflection coating. Notice that for such a solar cell PC1D predicts a photocurrent density around 17 mA/cm 2 , which is in good agreement with the experimental value.…”

“…Such interesting properties can be useful for solar cells and several papers have been published that dealt with the use of monocrystalline n-type silicon with junctions made by boron or aluminium in-diffusion. The Ebarra group has intensively investigated n-type monocrystalline silicon ribbon solar cells in which a rear junction was made by means of aluminium-silicon alloying [9,10]. This technique is very attractive because it is well known that in-diffusion of aluminium in silicon occurs at relatively low temperatures after the formation at 570 • C of the Al-Si eutectic alloy, which behaves like a metal.…”