Achieving Tunable Cold/Warm White-Light Emission in a Single Perovskite Material with Near-Unity Photoluminescence Quantum Yield.

Highlights: High-quality Sn²⁺/Mn²⁺-co-doped Rb₄CdCl₆ single crystals and powders were prepared and showed high-performance dual-emission white light with near-unity photoluminescence quantum yield. Short-range and extremely strong interactions between Sn²⁺ and Mn²⁺ were observed that lead to an intriguing ultra-high-efficiency Dexter energy transfer process from adjacent Sn²⁺ ions to Mn²⁺ ions. The dual-emission intensities were tuned flexibly by varying the fractions of Sn²⁺ and Sn–Mn pairs to balance their emission proportions for cold/warm white-light generation. Single materials that exhibit efficient and stable white-light emission are highly desirable for lighting applications. This paper reports a novel zero-dimensional perovskite, Rb₄CdCl₆:Sn²⁺_, Mn²⁺, which demonstrates exceptional white-light properties including adjustable correlated color temperature, high color rendering index of up to 85, and near-unity photoluminescence quantum yield of 99%. Using a co-doping strategy involving Sn²⁺ and Mn²⁺, cyan-orange dual-band emission with complementary spectral ranges is activated by the self-trapped excitons and d-d transitions of the Sn²⁺ and Mn²⁺ centers in the Rb₄CdCl₆ host, respectively. Intriguingly, although Mn²⁺ ions doped in Rb₄CdCl₆ are difficult to excite, efficient Mn²⁺ emission can be realized through an ultra-high-efficient energy transfer between Sn²⁺ and Mn²⁺ via the formation of adjacent exchange-coupled Sn–Mn pairs. Benefiting from this efficient Dexter energy transfer process, the dual emission shares the same optimal excitation wavelengths of the Sn²⁺ centers and suppresses the non-radiative vibration relaxation significantly. Moreover, the relative intensities of the dual-emission components can be modulated flexibly by adjusting the fraction of the Sn²⁺ ions to the Sn–Mn pairs. This co-doping approach involving short-range energy transfer represents a promising avenue for achieving high-quality white light within a single material. [ABSTRACT FROM AUTHOR]