Electronic Dimensionality Control of Exciton Localization in Lead-Free Copper Halide Perovskite Derivatives for Full-Color, High-Fidelity, and Circadian-Tunable White-Light Emission

Abstract

Rare-earth-free white light–emitting diodes (WLEDs) require emissive materials that simultaneously deliver high photoluminescence efficiency, spectral complementarity, and environmental stability. Here, an electronic-dimensionality-guided design strategy is reported for lead-free copper halide perovskite derivatives, in which emission color is set by Cu–halide connectivity and not by dopant chemistry, giving a predictive rule that spans both 0D and 1D frameworks. 0D Cs₃Cu₂I₅ and 1D CsCu₂X₃ (X═Cl, I) are synthesized via solution and low-temperature solid-state routes, producing blue, green, and yellow emissions with photoluminescence quantum yields up to ≈100%. Despite comparable bandgaps, distinct emission colors originate from dimensionality- and halide-dependent self-trapped exciton relaxation. By integrating these complementary emitters, WLEDs with a color rendering index of 96.6, a color quality scale of 98, and widely tunable correlated color temperatures (CCTs) are achieved by employing an ultrafast imprinting technique. The wide CCT tunability simultaneously enables human-centric lighting functionality, with the circadian action factor (CAF) tunable from 0.489 (evening-friendly) to 1.184 (daytime-alerting) and high color fidelity indices (CFI 91.0–95.8) across the full range, establishing this platform for circadian-supportive solid-state lighting.