Transparent luminescent solar concentrator (LSC) is extensively regarded as the most promising sunlight tapping device for its application in buildings integrated with photovoltaics (BIPV) or as solar window glass.Conventional LSCs doped with organic dyes suffered from high reabsorption losses with no trans-parency;whereas,recently reported heavy metal-doped quantum dots avoided such losses but possessed the risk of high toxicity and low ambient stability.Thus,luminophores with massive spectral shifts and cordial relationships with the environment are very much desirable.In this paper,we report the fabrication of PMMA based transparent LSC embedded with nanocrystals of environmental friendiness and multi-spectral harvesting gadolinium oxysulphide (Gd2O2S∶Er,Yb) fluorophore.The Gd2O2S∶Er,Yb nano-fluorophore absorbs various excitation wavelengths ranging from UV to NIR and emits in the visible region offering huge Stoke\'s and anti-Stoke\'s shift concurrently.The non-existent reabsorption losses and over-lapping maxima of Gd2O2S∶Er,Yb nanofluorophore generated photon flux with solar cells\' responsivity enhance the efficiency characteristics of the LSC waveguide.Performance analysis of LSC as a function of varying nanofluorophore dispersion ratio and changing edge width optimizes the fabrication process and exhibits high power conversion efficiency of ～6.93％ and optical efficiency of～8.57％.The LSC slab dem-onstrates high photostability under irradiation for prolonged hours without any dip in the emission characteristics.The Gd2O2S∶Er,Yb nanofluorophore diffused LSC waveguide offering spectral tunability,cost-reduction,efficiency enhancement,and high concentration factor whilst being sustainable for long term use makes it a fascinating transparent solar window.