Alkali metal salt-assisted crystal structure switch of hybrid indium halides with near-unity photoluminescence quantum yield

Abstract

In-based metal halides possess unique structures and optoelectronic properties but suffer from low luminescence efficiency. Rational doping and compositional control are effective approaches for achieving high-efficiency and tunable emissions in In-based metal halides. Here, we synthesized MA₄InCl₇ and MA₂KInCl₆ metal halides with 0D electronic dimensionality. Sb³⁺ doping enables bright orange and cyan emissions in MA₄InCl₇ and MA₂KInCl₆ at 587 and 490 nm, respectively, with high photoluminescence quantum yields (PLQYs) of 91% and 99%. Spectral technology and first-principles calculations reveal that different color emissions in these two metal halides originate from Sb³⁺-modulated self-trapped excitons (STEs) with different degrees of distortion of the excited state structures. Moreover, a one-way switch from MA₄InCl₇ to MA₂KInCl₆ can be achieved by adding additional potassium precursors. These findings shed light on the relationship between the structure and optical properties of metal halides and provide insights for designing new high-performance lead-free metal halides.