Spectrally Complementary Tandem Luminescent Solar Concentrators: Optical, Electrical and Stability Assessment

In this work, large-area tandem laminated double-layer luminescent solar concentrators (LSCs) based on blue-emitting and orange-emitting pyrene-derived graphitized carbon quantum dots (CQDs) dispersed in an ethylene–vinyl acetate (EVA) matrix were fabricated and systematically investigated. The optical properties and outdoor photovoltaic performance of the individual LSCs were evaluated and compared with those of the tandem architecture. The orange-emitting LSC exhibited a larger Stokes shift (≈135 nm) than the blue-emitting LSC (≈80 nm), indicating reduced spectral overlap and, consequently, lower self-absorption losses. Outdoor exposure revealed excellent short-term stability for the blue-emitting LSC, whereas the orange-emitting LSC exhibited a progressive decline in photovoltaic performance. The tandem architecture broadened the spectral harvesting range, achieving a maximum optical efficiency of 8.09% and a power conversion efficiency of 0.306% when illuminated from the orange-emitting LSC side. These results highlight tandem integration of spectrally complementary luminescent materials as a promising strategy for broadening solar-spectrum utilization and improving the optical and photovoltaic performance of LSCs, with potential for application in building-integrated photovoltaics (BIPVs).