Abstract
Y(or La)-doped NiO electrochromic materials with high electrochromic properties was designed by first‑principles calculations and synthesis successfully.
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•Theory-experiment closed loop enables rational design of doped NiO electrochromics.•DFT screening identifies Y as the optimal dopant over La and Ce.•Y-doped NiO exhibits 50.6 % optical modulation and fast switching kinetics.•High coloration efficiency of 215.6 cm2·C⁻1 is achieved experimentally.•Y-doped smart windows achieve 11.3 °C cooling, proving energy savings.
Doping is an effective strategy to tailor NiO for high‑performance eletrochromic applications. In this work, first‑principles calculations reveal negative formation energies for Y (−5.83 eV) and La (−3.72 eV) in NiO, confirming spontaneous and stable doping. Experimentally, Y and La doping dramatically boost the charge storage capacity of crystalline NiO films. Most notably, at 500 nm, the Y‑doped (Y‑4) and La‑doped (La‑4) films achieve outstanding optical modulations of 50.6 % and 32.0 %, respectively. They far exceed the 8.3 % of undoped NiO‑400. The doped films also exhibit much faster switching kinetics: coloration/bleaching time of 4.2/6.1 s for Y‑doped and 8.0/4.3 s for La‑doped, compared to 7.0/6.5 s for undoped NiO. More importantly, they exhibit remarkably high coloration efficiencies of 215.6 and 262.0 cm2·C−1, respectively. After 1000 cycles, the Y‑doped film retains 88.0 % of its initial charge capacity, and the La‑doped film retains 90.7 %. Model house tests indicate their good thermal insulation performance for building applications. This strategy of integrating computational design with experimental validation provides a powerful and general approach to develop tailored doped‑NiO electrochromic materials and other advanced functional materials.