Unprecedented hybrid lead bromides featuring trivalent aromatic cation for potential photodetection

Abstract

Organic cations, as charge compensators, balance the negative charge of lead halide anions through soft interaction forces, which have a significant impact on the crystal structure and electronic structure of hybrid lead halides. However, previous studies have mainly focused on monovalent and bivalent cations, and the use of trivalent cations in the synthesis and structure-activity relationship of hybrid lead halides has rarely been explored. Herein, two organic-inorganic hybrid lead bromines with trivalent aromatic cations were successfully synthesized, namely (H3tib)2Pb3Br12·H2O (1) and (H3tib)Pb2Br7 (2) (tib = 1, 3, 5-tri(1H-imidazol-1-yl)benzene). X-ray single-crystal diffraction techniques show that the crystal structures of 1 and 2 contain previously unreported (Pb3Br12)6− two-dimensional anion layer and (Pb2Br7)3− one-dimensional anionic chain, respectively. 1 is characterized by an indirect band gap with a band gap value of 3.04 eV, while 2 is characterized by a direct band gap with a value of 3.25 eV. The photocurrent switching ratio of 1 under visible light reaches 20.0, indicating its great potential in photodetection. Through Hirshfeld surface analysis and density functional theory (DFT) calculations, the electronic and band structure characteristics of the two compounds were discussed in depth.