In Figure 3e–3f, the three devices (i.e., Ca,C b and Cc) have been designed, a polycarbonate plate (PC plate, refractive index: 1.59) is employed as the light guider layer to gather scattering light to poly- silicon solar cells. In Figure 3e-Ca, the low reflective index medium for the device Ca (Figure 3b) and Cb (Figure 3c) was a VO2 particle film on a quartz plate and VO2-based power arrays, respectively.The latter was designed as a core-shell-shell structure (i.e., VO2@SiO2@ TiO2) to decrease the absorption of VO2 while maintaining the over- all size of the particles to fulfil the scattering conditions26. In Figure 3f, the low reflective index medium for the device Cc (Figure 3d) was a smooth VO2 thin film. The thickness of the PC is about 4 mm and thickness of the low reflective index medium is about 200 nm in these devices.