Reabsorption-free luminescent solar concentrator based on environmentally friendly cesium copper halide nanocrystals

Luminescent solar concentrator (LSC) based on colloidal nanocrystals (NCs) is the key component of building integrated photovoltaics (BIPVs). But strong reabsorption effect, or expensive/toxic components (e.g., In, Cd, or Pb) included in NCs hinder their applications. In this study, we fabricated low-cost, non-toxic LSCs based on cesium copper halide (Cs 3 Cu 2 X 5 , X = I or Cl) NCs. These materials possessed highly efficient self-trapped exciton emission with a large Stokes shift, with the consequent LSCs exhibiting clear reabsorption-free features with edge efficiencies close to the theoretical limits (∼70%) with varying device sizes. Furthermore, waveguiding PV devices consisting of above LSCs (8 × 8 × 0.5 cm 3 ) and commercial polysilicon PV cells exhibit power conversion efficiencies (PCEs) of up to 1.8%. In addition to the waveguiding effect on luminescent photons, these excellent PCEs were confirmed induced by the scattering of visible solar photons. These results clearly illustrated the photon propagation mechanism in LSCs based on Cs 3 Cu 2 X 5 NCs or similar colloidal NCs. The obtained PCEs in the range 0.8%–2.0% imply considerable potential for fabricating practical PV products with high output per Si PV unit area and low cost.