Figure 4. Tracking performance for GaAs kirigami trackers.

(a) Integrated thin-film, crystalline GaAs solar cells, mounted by cold weld bonding on a Kapton carrier substrate, as used for testing. Here, L_C=15 mm, x=5 mm and y=5 mm (R₁=R₂=3). (b) Normalized solar cell short circuit current density J_SC(φ)/J_SC(φ=0) for two samples, where R₁=R₂=3 and R₁=R₂=5 (closed symbols). Also shown are the simulated data for coupling efficiency (η_C) obtained from equation (4) (solid lines, open symbols). The agreement between experimental and simulated results suggests that η_C is a direct measure of optical coupling, and that performance may be optimized by increasing R₁ and R₂. (c) Output electrical power density incident on the solar cell versus time of day for several kirigami cut structures, stationary panel and single-axis tracking systems in Phoenix, AZ (33.45° N, 112.07° W) during the summer solstice. Inset: Integration of the curves yields the associated energy densities, where kirigami-enabled tracking systems are capable of near single-axis performance.