Enhancing the spectral tunability of localized surface plasmon resonance and small polaron transfer in Li-doped Cs WO3 nanocrystals for energy-efficient windows

CsxWO3 nanocrystals which exhibit localized surface plasmon resonance (LSPR) and small polaron transfer in wavelength of the near-infrared radiation have attracted great attention to fabricate the spectrally selective coating. Enhancing the LSPR and small polaron transfer of CsxWO3 nanocrystals is effectively achieved by introducing aliovalent dopant into its empty trigonal tunnels of the crystal lattice, but the lack of controllable synthesis process reserves some essential issues unanswered with respect to the effects of the dopant concentration on absorption coefficient, free carrier density and carrier mobility. Herein, Li-doped CsxWO3 nanocrystals were successfully prepared with the highest reported absorption coefficient, which demonstrated stronger absorption performance than the CsxWO3 nanocrystals without Li doping. The introduction of lithium into the crystal structure as a cation dopant can enhance the free carrier density of the nanocrystals, which leads to a higher absorption coefficient. The absorption coefficient variation of LSPR and small polaron transfer of Li-doped CsxWO3 nanocrystals was explained by the free carrier density and carrier mobility. This doping strategy allows CsxWO3 nanocrystals to become spectrally tunable within the wavelength of near-infrared radiation. When the Li/W molar ratio was 0.4, the free carrier density reached 10.22 × 1014 cm−3. The spectrally selective coating prepared by Li-doped CsxWO3 nanocrystals displayed excellent spectral selectivity with TVis, TNIR, Tlum, and Tsol of 68.79 %, 9.17 %, 72.61 % and 47.95 %, respectively. This doping strategy provides a promising potential to improve the spectral tunability of CsxWO3 nanocrystals for the practical application of energy-saving windows.