Realization of Flexible Large-Sized GaInP/GaAs/InGaAs Solar Cells With Stable Low-Temperature Ohmic Contact Technique

In the case of the fabrication of flexible solar cells based on the inverted metamorphic multijunction (IMM) structure, the conventional high-temperature annealing will result in the thin-film epitaxial layer warp or even crack, which could seriously affect the yield of flexible solar cells. The poor device fabrication processing compatibility arises from the large difference in thermal expansion coefficients between the ultrathin epitaxial layer and the flexible substrate. In this work, we developed the PdGe electrode to achieve the specific contact resistivity of 3.4 \times 10 ^{-\text{6}} \Omega \cdot cm ^{\text{2}} with low-temperature annealing. Thermal cycle tests have demonstrated the ultrahigh stability of the ohmic contact performance. By the employment of the designed electrode, the flexible large-sized GaInP/GaAs/InGaAs solar cells were successfully fabricated with a conversion efficiency of 35.37% under the AM1.5G illumination. The encapsulated flexible solar cells can remain above 98% of initial performance under the circumstance of 85 ^{\circ} C and 85% relative humidity. The stable and reliable electrode based on low-temperature annealing technology will greatly improve the production yield in the preparation of flexible electronic devices.