Spectrally Matched Quantum Dot Photoluminescence in GaAs-Si Tandem Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) can capture both direct and diffuse irradiance via isotropic absorption of waveguide-embedded luminophores. Additionally, LSCs have the potential to reduce the overall cost of a photovoltaic (PV) module by concentrating incident irradiance onto an array of smaller cells. Historically, LSC efficiencies have suffered in part from incomplete light absorption and non-unity quantum yield (QY) of the luminophores. Inorganic quantum dot (QD) luminophores allow the spectral tuning of the absorption and photoluminescence bands, and have near-unity QYs. In a four-terminal tandem LSC module scheme, visible light is trapped within the LSC waveguide and is converted by GaAs cells, and near infrared light is optically coupled to a Si subcell. Here, we investigate the efficiency of a GaAs/Si tandem LSC as a function of luminophore absorption edge and emission wavelength for QD luminophores dispersed in an LSC waveguide with embedded, coplanar GaAs cells. We find that positioning the luminophore absorption edge at 660 nm yields a maximum module power efficiency of approximately 26%, compared with 21% for the non-optimized luminophore and 19% for the bare Si cases.