Haoran Lin

A Zero‐Dimensional Organic Seesaw‐Shaped Tin Bromide with Highly Efficient Strongly Stokes‐Shifted Deep‐Red Emission

The synthesis and characterization is reported of (C9 NH20 )2 SnBr4 , a novel organic metal halide hybrid with a zero-dimensional (0D) structure, in which individual seesaw-shaped tin (II) bromide anions (SnBr42- ) are co-crystallized with 1-butyl-1-methylpyrrolidinium cations (C9 NH20+ ). Upon photoexcitation, the bulk crystals exhibit a highly efficient broadband deep-red emission peaked at 695 nm, with a large Stokes shift of 332 nm and a high quantum efficiency of around 46 %. The unique photophysical properties of this hybrid material are attributed to two major factors: 1) the 0D structure allowing the bulk crystals to exhibit the intrinsic properties of individual SnBr42- species, and 2) the seesaw structure enabling a pronounced excited state structural deformation as confirmed by density functional theory (DFT) calculations.

Highly Efficient Broadband Yellow Phosphor Based on Zero-Dimensional Tin Mixed-Halide Perovskite

Organic-inorganic hybrid metal halide perovskites have emerged as a highly promising class of light emitters, which can be used as phosphors for optically pumped white light-emitting diodes (WLEDs). By controlling the structural dimensionality, metal halide perovskites can exhibit tunable narrow and broadband emissions from the free-exciton and self-trapped excited states, respectively. Here, we report a highly efficient broadband yellow light emitter based on zero-dimensional tin mixed-halide perovskite (C4N2H14Br)4SnBrxI6-x (x = 3). This rare-earth-free ionically bonded crystalline material possesses a perfect host-dopant structure, in which the light-emitting metal halide species (SnBrxI6-x4-, x = 3) are completely isolated from each other and embedded in the wide band gap organic matrix composed of C4N2H14Br-. The strongly Stokes-shifted broadband yellow emission that peaked at 582 nm from this phosphor, which is a result of excited state structural reorganization, has an extremely large full width at half-maximum of 126 nm and a high photoluminescence quantum efficiency of ∼85% at room temperature. UV-pumped WLEDs fabricated using this yellow emitter together with a commercial europium-doped barium magnesium aluminate blue phosphor (BaMgAl10O17:Eu2+) can exhibit high color rendering indexes of up to 85.

Manganese-Doped One-Dimensional Organic Lead Bromide Perovskites with Bright White Emissions

Single-component white-emitting phosphors are highly promising to simplify the fabrication of optically pumped white light-emitting diodes. To achieve white emission, precise control of the excited state dynamics is required for a single-component system to generate emissions with different energies in the steady state. Here, we report a new class of white phosphors based on manganese (Mn)-doped one-dimensional (1D) organic lead bromide perovskites. The bright white emission is the combination of broadband blue emission from the self-trapped excited states of the 1D perovskites and red emission from the doped Mn2+ ions. Because of the indirect nature of the self-trapped excited states in 1D perovskites, there is no energy transfer from these states to the Mn2+ ions, resulting in an efficient dual emission. As compared to the pristine 1D perovskites with bluish-white emission, these Mn-doped 1D perovskites exhibit much higher color rendering index of up to 87 and photoluminescence quantum efficiency of up to 28%.

Organic–inorganic metal halide hybrids beyond perovskites

ABSTRACT Organic–inorganic metal halide hybrids have emerged as new generation functional materials with exceptional structure and property tunability for a variety of applications. Besides the most investigated ABX3 metal halide perovskites, a variety of hybrids consisting of a wide range of organic cations and metal halide anions have been developed and studied recently. Here, we provide an overview of these new materials possessing various crystallographic structures, including double perovskites, low dimensional hybrids, and other perovskite-related materials. We discuss their syntheses, functional properties, and optoelectronic applications. Challenges and opportunities are then laid out for these hybrid materials beyond perovskites. GRAPHICAL ABSTRACT IMPACT STATEMENT By choosing appropriate organic cations and metal halide anions, single crystalline ionically bonded hybrid materials can be assembled to possess various structures beyond the well-known ABX3 perovskite. These hybrid materials exhibit exciting new properties with potential applications in a variety of areas.

Blue Emitting Single Crystalline Assembly of Metal Halide Clusters

The rich chemistry of organic-inorganic metal halide hybrids has enabled the development of a variety of crystalline structures with controlled morphological and molecular dimensionalities. Here we report for the first time a single crystalline assembly of metal halide clusters, (C9NH20)7(PbCl4)Pb3Cl11, in which lead chloride tetrahedrons (PbCl42-) and face-sharing lead chloride trimer clusters (Pb3Cl115-) cocrystallize with organic cations (C9NH20+) to form a periodical zero-dimensional (0D) structure at the molecular level. Blue light emission peaked at 470 nm with a photoluminescence quantum efficiency (PLQE) of around 83% was realized for this single crystalline hybrid material, which is attributed to the individual lead chloride clusters. Our discovery of single crystalline assembly of metal halide clusters paves a new path to functional cluster assemblies with highly tunable structures and remarkable properties.

Direct Evidence of Exciton–Exciton Annihilation in Single-Crystalline Organic Metal Halide Nanotube Assemblies

Excitons in low-dimensional organic-inorganic metal halide hybrid structures are commonly thought to undergo rapid self-trapping following creation due to strong quantum confinement and exciton-phonon interaction. Here we report an experimental study probing the dynamics of these self-trapped excitons in the single-crystalline bulk assemblies of 1D organic metal halide nanotubes, (C6H13N4)3Pb2Br7. Through time-resolved photoluminescence (PL) measurements at different excitation intensities, we observed a marked variation in the PL decay behavior that is manifested by an accelerated decay rate with increasing excitation fluence. Our results offer direct evidence of the occurrence of an exciton-exciton annihilation process, a nonlinear relaxation phenomenon that takes place only when some of the self-trapped excitons become mobile and can approach either each other or those trapped excitons. We further identify a fast and dominant PL decay component with a lifetime of ∼2 ns with a nearly invariant relative area for all acquired PL kinetics, suggesting that this rapid relaxation process is intrinsic.