Single crystalline bulk assemblies of metal halide clusters exhibit great potential as highly efficient light emitters with tunable photophysical properties. However, it is not trivial to synthesize metal halide clusters with controlled size and geometry due to the lack of rational design rules. And the structure-property relationships for this class of hybrid materials have not been well established yet. Here, by carefully optimizing the synthesis conditions, we have developed two different 0D organic metal halide clusters, (bmpy)6[Pb3Br12] (T1) and (bmpy)9[ZnBr4]2[Pb3Br11] (T2), where T1 contains chain-shaped [Pb3Br12]6− units and T2 contains triangle-shaped [Pb3Br11]5− units. Interestingly, T1 is not emissive at room temperature, while T2 emits yellowish-green light peaked at 564 nm with a photoluminescence quantum efficiency (PLQE) of 7%. Detailed structural and photophysical studies show that the photophysical properties of these materials are highly dependent on the geometry of metal halide clusters with multiple excited state structures. The photoluminescence of these materials also exhibits strong dependence on the environmental conditions, improving significantly with the decreasing of temperature or applying high pressure. Our work clearly shows the rich chemistry and photophysics of organic metal halide clusters as an emerging class of hybrid materials.

Zero-dimensional lead bromide clusters with geometry-dependent photophysical properties

ACS Fall 2021

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