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2D Dion–Jacobson (2D DJ) perovskites are considered as promising photovoltaic materials due to their structural stability and spacer designability. Here, a spacer cation with an aromatic imidazole ring, 2‐(1H‐imidazol‐2‐yl)ethylammonium (HE), is successfully applied to construct 2D DJ perovskite. It's found that the high polarity of the HE spacer strengthens the interaction between organic and inorganic layers and reduces the exciton binding energy to 67.8 meV, resulting in promoted charge dissociation, compared with the aliphatic 1,4‐butanediammonium (BDA) spacer with a similar length. The HE spacer enlarges the micelle size in precursor solution and suppresses the formation of low‐n value phases. In consequence, the HE‐based perovskite film exhibits better quality than the BDA‐based one, with lower defect density and longer carrier lifetime. The optimized device based on (HE)(MA0.75FA0.25)4Pb5I16 film achieves a champion power conversion efficiency up to 18.40%, much higher than that of the BDA‐based device (15.03%). Besides, the unencapsulated device based HE exhibits improved moisture and thermal stability. [ABSTRACT FROM AUTHOR]

A series of lead-free Rb2ZrCl6:xTe4+ (x = 0%, 0.1%, 0.5%, 1.0%, 2.0%, 3.0%, 5.0%, 10.0%) perovskite materials were synthesized through a hydrothermal method in this work. The substitution of Te4+ for Zr in Rb2ZrCl6 was investigated to examine the effect of Te4+ doping on the spectral properties of Rb2ZrCl6 and its potential applications. The incorporation of Te4+ induced yellow emission of triplet self-trapped emission (STE). Different luminescence wavelengths were regulated by Te4+ concentration and excitation wavelength, and under a low concentration of Te4+ doping (x ≤ 0.1%), different types of host STE emission and Te4+ triplet state emission could be achieved through various excitation energies. These luminescent properties made it suitable for applications in information encryption. When Te4+ was doped at high concentrations (x ≥ 1%), yellow triplet state emission of Te4+ predominated, resulting in intense yellow emission, which stemmed from strong exciton binding energy and intense electron-phonon coupling. In addition, a Rb2ZrCl6:2%Te4+@RTV scintillating film was fabricated and a spatial resolution of 3.7 lp/mm was achieved, demonstrating the potential applications of Rb2ZrCl6:xTe4+ in nondestructive detection and bioimaging. [ABSTRACT FROM AUTHOR]

A library of large organic cation spacers is available for engineering the performance of layered two‐dimensional (2D) halide perovskite devices. Despite extensive photophysics studies, there remains a research gap over the structure‐function relations in 2D perovskites, especially the underlying factors influencing the Auger recombination (AR) process. Herein, the contributions of exciton binding energy, exciton‐phonon coupling, and defects/film morphology to the AR process in 2D perovskites are examined. Phenyl‐alkyl‐ammonium cations with different lengths of attached alkyl groups, commonly used in blue light‐emitting diodes, are investigated. The findings reveal an order of magnitude higher threshold carrier density for the AR onset as well as a reduced AR in cations with longer alkyl chain length. Although possessing similar exciton binding energies, the exciton‐phonon coupling strength is found to play a major role in reducing the AR rate, with a smaller contribution from the defect states/film morphology. The findings can help provide further guidance on organic spacer cation engineering for highly efficient 2D perovskite light emitters. [ABSTRACT FROM AUTHOR]