Triplet–triplet energy transfer from Bi3+ to Sb3+ in zero-dimensional indium hybrids via a B-site co-doping strategy toward white-light emission

Abstract

Low-dimensional metal halides have emerged as promising platforms for the development of new-generation phosphor-converted light emitting diodes (pc-LEDs), in which zero-dimensional (0D) hybrids with lone-pair ns² states, in particular, show unprecedented competitiveness owing to their fascinating photoluminescence (PL) properties. Herein, we designed a novel 0D indium hybrid, (C₂₀H₂₀P)₂InCl₅, and proposed a co-doping strategy to incorporate Bi³⁺ (6s²) and Sb³⁺ (5s²) ions into this indium hybrid. Widely tunable emissions from blue to red are achieved, which are assigned to the triplet self-trapped excitons (STEs) (³P₁ → ¹S₀) of Bi³⁺ (476 nm) and Sb³⁺ (658 nm), respectively. Importantly, an uncommon triplet–triplet energy transfer from Bi³⁺ to Sb³⁺ contributes to tunable dual emissions, and enables a single-phase cool white-light emission under ultraviolet (UV) excitation. Moreover, the energy transfer mechanism is discussed clearly by fluorescence photon dynamic analysis and DFT calculations. This work provides a deeper insight into triplet–triplet energy transfer, as well as presents a new model system for tuning the PL behaviours of ns² configuration dopants.