2D hybrid lead halide perovskites exhibit versatile photoluminescent behaviors for narrowband to broadband emissions (BBEs) and have become attractive candidates for potential applications such as solid-state lighting. Establishing the relationship between the perovskite structural distortion and BBE is key but challenging in designing and optimizing the perovskite luminophores. Conventional attention is given to analyzing the intra-octahedron distortion of the [PbX6]4– (X = halide) unit that has not yet provided a clear structure–luminescence relationship. Herein, we introduce a descriptor, Pb displacement, to describe the inter-octahedron distortion to clarify the structure–emission relationship. The displacement of adjacent Pb centers represents the lattice distortion, which determines the broadband/narrowband emission instead of the octahedron distortion itself. We find a kite-type quadrilateral rule in (001) type 2D perovskites, that is, the degree to which the four octahedral central ions deviate from a square relates to the BBE. The kite-type arrangement of the Pb ions usually corresponds to the BBEs due to the large structure distortions. In contrast, the square-type arrangement of the Pb ions corresponds to the narrowband emissions because of the small distortions. The distortion descriptor magnifies the distortion scale, making it larger than the conventional one for the intra-octahedron distortion, which matches the general concept of excitons based on the scale of the crystal lattice. Therefore, the set of structural descriptors is better to correlate the perovskite structures and emission properties.

halide perovskites (LDHPs), the optically active inorganic blocks are separated and surrounded by insulating organic components with intrinsic quantum confinement effects, which readily leads to firmly confined bound excitons in the metal halide species under photo excitation. Simultaneously, the strong electronquantum coupling transiently localizes the excitons along with excited-state structural deformation, which produces selftrapped excitons (STE) with lower excited state energy. [4] Therefore, the bulk LDHPs always display strongly Stokes-shifted broadband light emissions, which are different from the narrow emission bands of 3D halide perovskites. [5] These distinctive luminescent performances endow LDHPs with a series of unique applications complementary to the 3D perovskites in solid-state lighting, X-ray scintillation, remote thermometry, and thermography, especially for white light emitting diodes (WLEDs). [6] Among all the PL qualities, PL quantum yield (PLQY) is one of the most important indicators for optoelectronic applications of hybrid halide perovskites. To achieve higher PLQY and more desirable luminescence performance, substantial optically active centers based on ns 2 electronic configuration of valence shell have been explored including Sn 2+ , Ge 2+ , Pb 2+ , Bi 3+ , and Sb 3+ . [7][8][9] In these fascinating hybrid metal halides, the 5s 2 metal halides readily occupy the maximum of emission efficiency owing to the unique expressed structural distortion level induced by the out shell lone pair. [10] Simultaneously considering the instabilities of Sn 2+ and Ge 2+ halides, toxicity of Pb 2+ , metal as well as low efficiencies of Bi 3+ phases, green 5s 2 Sb 3+ based hybrid metal halides are deemed to be one of most promising ultrabroadband luminescent materials with higher PLQYs and oxidation resistance abilities. [7b,8a,11] Up to now, the PLQYs of 0D hybrid antimony halides based on discrete [SbX 5 ] 2− and [SbX 6 ] 3− units can reach up to near unity due to strong quantum confinement effect. [12] These outstanding PL properties intrigued further in-depth understanding the enhancement or modulating mechanism of PLQY for hybrid antimony halides from molecular design level, which is also greatly desirable for subsequent rational design of new high-performance hybrid halides. Rationally optimizing the photoluminescence performance via accurate structural modulation is one of most important and challenging issues for hybrid halides. Herein, a viable crystal dimensional reduction strategy is proposed to reasonably enhance the photoluminescence quantum yield (PLQY) of hybrid antimony halide. Specifically, a synthetic technique is developed and new 1D [DMPZ]SbCl 5 • H 2 O (DP-SbCl 5 ) is sliced to 0D [DMPZ] 2 SbCl 6 • Cl • (H 2 O) 2 (DP-SbCl 6 ) with crystal dimensional reduction from infinite [SbCl 5 ] 2− chain to discrete [SbCl 6 ] 3− octahedron. Comparing with nonluminescent 1D DP-SbCl 5 , 0D DP-SbCl 6 displays highly efficient broadband yellow light emission with enhanced PLQY up to 75.94%. ...

Recently, 2D organic–inorganic hybrid lead halide perovskites have attracted intensive attention in solid‐state luminescence fields such as single‐component white‐light emitters, and rational optimization of the photoluminescence (PL) performance through accurate structural‐design strategies is still significant. Herein, by carefully choosing homologous aliphatic amines as templates, isotypical perovskites [DMEDA]PbCl4 (1, DMEDA=N,N‐dimethylethylenediamine) and [DMPDA]PbCl4 (2, DMPDA=N,N‐dimethyl‐1,3‐diaminopropane) having tunable and stable broadband bluish white emission properties were rationally designed. The subtle regulation of organic cations leads to a higher degree of distortion of the 2D [PbCl4]2− layers and enhanced photoluminescence quantum efficiencies (<1 % for 1 and 4.9 % for 2). The broadband light emissions could be ascribed to self‐trapped excitons on the basis of structural characterization, time‐resolved PL, temperature‐dependent PL emission, and theoretical calculations. This work gives a new guidance to rationally optimize the PL properties of low‐dimensional halide perovskites and affords a platform to probe the structure–property relationship.

Recently, two-dimensional (2D) hybrid lead halide perovskite has been widely utilized as a preferred platform of optoelectronic material with tailorable compositions, structures, and intrinsic broadband emission properties, and this achievement significantly promotes the research desirability to explore a new type of halide prototype to mimic the 2D perovskite model. Herein, we first performed a systematic approach on one-dimensional (1D) perovskite and realized comparable performances in both structural and property modulations. Specifically, by choosing diversified organic cations as a structural design strategy, we successfully constructed a series of 1D APbBr3 (A = DBU, 1,8-diazabicyclo[5.4.0]­undec-7-ene; DMTHP, 5,5-dimethyl-1,4,5,6-tetrahydropyrimidine; DBN, 1,5-diazabicyclo[4.3.0]-5-nonene; EPD, 1-ethylpiperidine) homologues based on identical 1D face-shared octahedral [PbBr3]− chains. This structural model features large accommodation ability for a variety of organic blocks enabling diversified photoluminescence (PL) properties from broadband yellow to white light emissions. Most remarkably, [DBU]­PbBr3 displays broadband yellow (0.47, 0.45) and white (0.32, 0.36) light emissions from two excited centers corresponding to distinct self-trapped excitons (STEs). These efficient dual light emissions were verified by high photoluminescence quantum yields (PLQYs) of 5.47 and 5.17%, respectively. The multiple advantages of unified crystal lattice, tailorable chemical composition, and tunable PL performance enable this 1D APbBr3 perovskite to be an emerging and standard structural prototype to diversify and optimize the optoelectronic properties with potential in single-component white-light-emitting diodes.