“…A microtracking concentrator photovoltaic system (MTCPV) that integrates a CPV and a solar tracker into a module is being developed [3]. Examples of MTCPV structures include (a) a two-lens structure on the top surface of a multijunction solar cell [4], (b) an upper waveguide and lens structure on a multijunction solar cell [5][6][7][8][9][10][11], (c) a structure combining an upside lens and a downside mirror on a multijunction solar cell [12,13], (d) a resin filled mirror under a solar cell stage [14], (e) a structure comprised of a wide angle aplanatic lens and a solar cell stage with three-dimensional control [15], and (f) a structure comprised of a gradient-index(GRIN) lens [16,17] and a solar cell stage with three-dimensional control [18]. Of these, structure (f) has yet to be experimentally demonstrated as it requires a gradient low-refractive index (RI) structure.…”