c-Si/n-ZnO based flexible solar cells with silica nanoparticles as light trapping metamaterial
Fabrication of flexible solar cells based on crystalline p-Si/n-ZnO heterostructure is being reported here for the first time. An enhancement ~ 52% of base efficiency was achieved by the application of spherical SiO2 nanoparticles as light trapping structures on the top. The use of ZnO not only offers a facile route of synthesis, but also provides an additional advantage of large band bending leading to notable open circuit voltage and formation of intermediate ultra-thin barrier layer of Zn2SiO4 for minimized carrier recombination. The spherical silica nanoparticles act as nano-resonators, causing absorption hot-spots in the thin silicon absorber, along with the capability of providing wide angle light collection. Simulation showed, for higher angle of incidence the silica nanoparticles have the ability to bend light on the same side of the normal to the incident wave-front, thereby acting as a negative index metamaterial (NIM). The flexibility of the device and cost effectiveness can make this concept important for next generation photovoltaics and roll-to-roll electronics.