Zn²⁺-doped Cs-Cu-I perovskite nanocrystals for white light-emitting diodes with high color rendering index

Cs-Cu-I perovskites have shown great potential in white light-emitting diodes (WLEDs) due to their unique self-trapped exciton (STE) radiative recombination with broad emission. However, their relatively low photoluminescence quantum yield (PLQY) limits practical applications. Here, we significantly enhance the PLQY of Cs₃Cu₂I₅ nanocrystals from 56% to 86% simply via Zn²⁺ aliovalent doping. Density functional theory calculations and temperature-dependent photoluminescence spectra reveal that Zn²⁺ preferentially occupies the tetrahedral Cu site, introducing a shallow defect level as an efficient radiative recombination center. Meanwhile, the Zn²⁺ doping increases the exciton binding energy to 309.5 meV and reconstructs electron–phonon coupling, thereby promoting the formation of STE. Furthermore, a white-emitting Cs-Cu-I mixture consisting of blue-emitting Cs₃Cu₂I₅ and yellow-emitting CsCu₂I₃ is obtained in situ via a one-pot method by adjusting the reaction temperature without post-synthesis ratio adjustment. Based on this, a WLED with Commission Internationale de l’Éclairage (CIE) coordinates of (0.31, 0.33) and a color rendering index (CRI) of 89.2 is fabricated. Moreover, double perovskite (Cs₂Na_1−xAg_xIn_1−yBi_yCl₆, λ_em = 622 nm) is introduced to compensate for the insufficient red emission. The resulting WLED achieves standard white light with CIE coordinates of (0.33, 0.33), a high CRI of 94.5, and a saturated red rendering index (R₉) value of 84. This device also exhibits excellent operational and environmental stability, along with an ultra-wide beam angle of 177°. This work not only clarifies the mechanism of ion doping in 0D perovskites but also provides a new pathway for constructing high-quality, environmentally friendly WLEDs for solid-state lighting.