Four-junction solar energy cell having reflection layer

Abstract

The invention discloses a four-junction solar energy cell having a reflection layer and can be applied to the focusing photovoltaic power generation system. According to the four-junction solar energy cell, a Ge single crystal slice is taken as a substrate, the Ge substrate is sequentially provided with a GaInAs / GaInP buffer layer, an AlGaAs / GaInAs DBR reflection layer, a GaInNAs sub cell, a GaInAs sub cell and a GaInP sub cell, wherein the AlGaAs / GaInAs DBR reflection layer is used for reflecting long-wave photons to make the long-wave photons be absorbed by the GaInNAs sub cell. Through the four-junction solar energy cell, thickness of the GaInNAs sub cell can be reduced, cell collection efficiency is improved, and photoelectric conversion efficiency of the four-junction solar energy cell is improved.

Description

technical field [0001] The invention relates to the technical field of solar photovoltaics, in particular to a four-junction solar cell with a reflective layer. Background technique [0002] Currently, traditional gallium arsenide multi-junction solar cells are widely used in concentrated photovoltaic (CPV) systems and space power systems because their conversion efficiency is significantly higher than that of crystalline silicon cells. The mainstream structure of gallium arsenide multi-junction solar cells is a GaInP / GaInAs / Ge triple-junction solar cell composed of GaInP, GaInAs and Ge sub-cells. The cell structure maintains lattice matching as a whole, and the bandgap structure is 1.85 / 1.40 / 0.67eV. However, for the solar spectrum, the bandgap combination of this triple-junction cell is not optimal due to the large bandgap gap between the GaInAs subcell and the Ge subcell, and the solar spectrum absorbed by the Ge bottom cell under this structure The energy absorbed by the...

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Problems solved by technology

[0004] In the actual preparation process of GaInNAs materials, due to the high price of the N source (usually dimethylhydrazine source) that provides N atoms, the thickness of the GaInNAs material layer should not be too thick, otherwise the material preparation cost will be very high; in addition, because GaInNAs needs Low temperature growth can ensure the effective incorporation of N atoms. Therefore, a large number of C atoms will be introduced into the material at the same time, resulting in too high background carrier concentration and affecting the minority carrier diffusion length. At this time, the material layer is too thick to form photogenerated carriers. effective collection of

However, if the thickness of the GaInNAs material layer is not enough, it cannot completely absorb the photons with a wavelength of 900-1200nm, and its current density will decrease, which seriously affects the photoelectric conversion performance of the four-junction cell.

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