A new class of solar cell with multi-layer structure

Abstract

A new class of silicon solar cell has been developed. The theory of this cell is described. The cell was fabricated by the epitaxial growth of npnpnp six layers on n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -type silicon subtrate and the p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> diffusion layer formed onto the top epitaxial n-layer. An oxygen-doped polycrystalline-silicon(SIPOS) layer which has the refractive index of 2 was deposited onto the cell as an antireflection film. The size of the cell was 0.8 × 0.8 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and about 20 % of the surface area was covered by a contact metal grid. The series resistance of this cell was measured to be 0.012Ω. In direct sunlight of 80 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at AM 1, the output power of the cell was 5.5 mW at 35 °C, which corresponded to 10.8 % in efficiency. By the effective concentration of 623 suns, the output power of the cell was 3.52 W at 56°C, corresponding to 11.1% in efficiency.