Recent progress of triplet state emission in organic-inorganic hybrid metal halides

Due to the high photoluminescence quantum yield (PLQY) and multiple-colored emissions by adjusting their composition and structures, organic-inorganic hybrid metal halides (MHs) have become promising emitters for next-generation light emitting and displays. When separate inorganic metal halides by larger organic cations in crystals, multiple low-dimensional MHs (LDMHs) at the molecular level can be constructed. These LDMHs have been widely reported to exhibit excellent photoluminescence properties which stems from radiative recombination of self-trapped excitons (STEs). Recently, efficient triplet state emission including room-temperature phosphorescence (RTP) originated from organic cations triplet states is also demonstrated in LDMHs, opening a new field for the development of phosphorescence emitters. Herein, we summarize and discuss the new progress in triplet state emission in LDMHs for a better understanding the RTP development of LDMHs for their versatile display applications.