Lecithin‐Enabled Emission Line‐Width and Chromaticity Stability Toward BT.2020‐Compatible Pure‐Red Perovskite Quantum Dots

Pure‐red perovskite quantum dots (PeQDs) are indispensable emitters for wide‐color‐gamut display applications owing to their intrinsically narrow emission line‐width and high photoluminescence quantum yield. A‐site cation exchange enables emission wavelength tuning without altering halide composition; however, it often introduces lattice strain and static disorder, resulting in spectral broadening and chromatic instability. Here, we elucidate the mechanistic role of lecithin in stabilizing pure‐red PeQDs during A‐site cation exchange through temperature‐dependent photoluminescence (320–240 K), quantitative 1 H NMR ligand analysis, and time‐resolved photoluminescence measurements. Lecithin‐assisted samples exhibit line‐width narrowing from 26.31 to 18.22 nm upon cooling, whereas nonassisted samples broaden from 59.31 to 82.64 nm, indicating dominant static inhomogeneous broadening. The chromaticity coordinates of the lecithin‐assisted PeQDs remain nearly unchanged under temperature variation and stay close to the BT.2020 red primary (0.708, 0.292), with a markedly reduced chromaticity shift (Δ xy = 0.0010), compared to nonassisted samples. Time‐resolved analysis reveals an extension of the slow decay component ( τ 2 ) from 22.03 to 35.19 ns upon lecithin incorporation, confirming suppression of disorder‐induced nonradiative recombination. These findings demonstrate that lecithin‐assisted A‐site cation exchange enables thermally robust line‐width and chromatic stability, providing a practical materials strategy for BT.2020‐compatible, high‐color‐purity red emitters.