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

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 ns(2) states, in particular, show unprecedented competitiveness owing to their fascinating photoluminescence (PL) properties. Herein, we designed a novel 0D indium hybrid, (C20H20P)(2)InCl5, and proposed a co-doping strategy to incorporate Bi3+ (6s(2)) and Sb3+ (5s(2)) ions into this indium hybrid. Widely tunable emissions from blue to red are achieved, which are assigned to the triplet self-trapped excitons (STEs) (P-3(1) -> S-1(0)) 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 ns(2) configuration dopants.