The Diffusion Effect of Copper on the Flexible GaInP/GaAs Solar Cells

Electroplating copper is widely used in the fabrication of flexible III-V multijunction solar cell because of its excellent characteristics of lightness, flexibility and conductivity of thin Cu, which can be directly applied as the flexible support and the external electrode. In this letter, we studied the diffusion effect of copper in the flexible GaInP/GaAs solar cells under high temperature annealing, which plays an essential role in achieving a promising ohmic contact between contact layer and metal. However, the degradation in the performance of flexible cell was observed when the annealing procedure was employed at the last step of the device fabricating process. The secondary ion mass spectrometry and electroluminescence results have indicated that the degradation of the solar cell performance after high-temperature annealing is attributed to the excess copper diffusion into active region of the solar cell. High temperature diffusion of copper can be solved by prior-annealing to form ohmic contact.