Silicon Quantum Dot Luminescent Solar Concentrators and Downshifters with Antireflection Coatings for Enhancing Perovskite Solar Cell Performance

In this work, we demonstrate a four-terminal tandem solar cell consisting of a luminescent solar concentrator (LSC) based on silicon quantum dots (SiQDs) in front of a 4 cm × 4 cm perovskite solar cell (PSC). The LSC front surface is uniformly covered with a nanoporous poly­(methyl methacrylate) (PMMA) antireflection coating, which can enhance the transmission by up to 3% from the visible to the near-infrared range. The colloidal SiQDs inside the LSC primarily absorb the UV portion of the solar irradiation, re-emitting red fluorescence, which propagates to the waveguide edges for generating electricity while allowing the rest of the incident sunlight to be absorbed in the back PSC. With an air gap between the SiQD-LSC and PSC, compared to the bare PSC, the two devices in combination exhibits significant external quantum efficiency (EQE) enhancement under 365 nm UV illumination, but shows no power conversion efficiency (PCE) enhancement under xenon arc lamp illumination. In contrast, when the air gap is removed, the SiQD-LSC becomes a luminescent downshifter than a concentrator, with most of the SiQD fluorescence being absorbed by the back PSC. In this case, the SiQD-LSC/PSC tandem solar cell can achieve up to 6.2% PCE enhancement over the bare PSC at low SiQD concentrations. Particularly, at 1.08 mg mL–1, although the tandem solar cell has about the same PCE as the bare PSC, the front SiQD-LSC absorbs 69% of the solar UV, making the back PSC more stable than the bare PSC.