This study presents a new laminated luminescent solar concentrator (LSC) structure that significantly enhances the efficiency of solar energy harvesting. The key innovation is the introduction of a patterned low-refractive-index medium (PLRM) that acts as an optical 'guard rail', providing a practically non-decaying path for guiding hot-cans. This design minimizes reabsorption by fluorophores and improves the external quantum efficiency (η_ext) and concentration factor (C-factor) of LSCs. The study also proposes design rules for the dimensions of LSCs and the spectral characteristics of fluorophores, leading to record-high performance. The measured η_ext at 450 nm for a 100 cm² area is 45%, and for an LSC with an edge aspect ratio of 71, it is 32%. The device efficiency is 7.6%, the highest ever reported. The study highlights the importance of minimizing reabsorption and optimizing the optical properties of the materials used. The results suggest that LSCs have significant potential for commercialization, particularly in building-integrated photovoltaic systems. The study also discusses the use of various fluorophores, including quantum dots and perovskites, and the role of the PLRM in enhancing the performance of LSCs. The findings indicate that the integration of a PLRM with a low-refractive-index medium can significantly improve the efficiency of LSCs, making them a promising technology for energy-harvesting windows in buildings.This study presents a new laminated luminescent solar concentrator (LSC) structure that significantly enhances the efficiency of solar energy harvesting. The key innovation is the introduction of a patterned low-refractive-index medium (PLRM) that acts as an optical 'guard rail', providing a practically non-decaying path for guiding hot-cans. This design minimizes reabsorption by fluorophores and improves the external quantum efficiency (η_ext) and concentration factor (C-factor) of LSCs. The study also proposes design rules for the dimensions of LSCs and the spectral characteristics of fluorophores, leading to record-high performance. The measured η_ext at 450 nm for a 100 cm² area is 45%, and for an LSC with an edge aspect ratio of 71, it is 32%. The device efficiency is 7.6%, the highest ever reported. The study highlights the importance of minimizing reabsorption and optimizing the optical properties of the materials used. The results suggest that LSCs have significant potential for commercialization, particularly in building-integrated photovoltaic systems. The study also discusses the use of various fluorophores, including quantum dots and perovskites, and the role of the PLRM in enhancing the performance of LSCs. The findings indicate that the integration of a PLRM with a low-refractive-index medium can significantly improve the efficiency of LSCs, making them a promising technology for energy-harvesting windows in buildings.