Nanocolloid simulators of luminescent solar concentrator photovoltaic windows

Transparent luminescent solar concentrator (LSC) windows with edge-attached photovoltaic (PV) cells have the potential for improving building efficiency without compromising aesthetics and comfort. Optimization of such windows requires an inexpensive simulator for experimenting with various designs. We report, for the first time to the best of our knowledge, the simulator of a transparent LSC window in the form of a plastic container filled with a colloid of photoluminescent nanoparticles (NPs) in an organic solvent (1-propanol). The exemplary NPs were produced by ball milling of the powder of rare earth (RE)-doped phosphor NaYF4:Yb3+,Er3+ synthesized by the wet method. The NPs converted the ultraviolet (UV) solar spectrum into visible/near infrared (NIR) via spectral down-shifting and down-conversion (quantum cutting). With a photoluminescence quantum yield (PLQY) of the phosphor <0.4%, the LSC at a nanocolloid concentration of similar to 0.1 g solids per 100 mL liquids demonstrated a power conversion efficiency of 0.34% and a power concentration ratio of similar to 0.022 comparable to the LSCs with RE-doped NPs with 200 times greater PLQY. At the same time, the 3 cm thick LSC window simulator had similar to 90% transmittance to the sunlight. The content and concentration of the nanocolloid could be easily modified to optimize the LSC window performance without a costly window making process.