Oxygen defect-induced small polaron transfer for controlling the near-infrared absorption coefficient of hexagonal cesium tungsten bronze nanocrystals

Hexagonal cesium tungsten bronze (Cs_xWO₃) nanocrystals have attracted great attention in the field of energy-efficient windows, which exhibit the localized surface plasmon resonance (LSPR) effect and small polaron transfer in near-infrared radiation (NIR). The enhancement of the LSPR effect can be achieved by introducing aliovalent dopant into the crystal lattice, but the improvement of small polaron transfer remains a challenge. Herein, Cs_xWO₃ nanocrystals with oxygen defects were successfully prepared by a facile one-pot method. The introduction of oleylamine in the precursor can induce the formation of oxygen defects in the crystal lattice, which leads to a higher absorption coefficient. The spectrally selective coating prepared by Cs_xWO₃ nanocrystals with oxygen defects exhibited superior spectral selectivity with T_Vis, T_NIR, T_lum, and T_sol of 67.11%, 11.21%, 72.59% and 49.12%, respectively.