34099-97-3Relevant academic research and scientific papers
Dynamic Motion of Organic Spacer Cations in Ruddlesden-Popper Lead Iodide Perovskites Probed by Solid-State NMR Spectroscopy
Dahlman, Clayton J.,Kennard, Rhys M.,Paluch, Piotr,Venkatesan, Naveen R.,Chabinyc, Michael L.,Manjunatha Reddy
, p. 642 - 656 (2021)
Layered hybrid organic-inorganic perovskites such as the lead halide Ruddlesden-Popper (RP) series are solution-processable two-dimensional (2D) materials with tunable optoelectronic properties. Dynamic interactions between the ionic perovskite substructure and organic spacer cations impact optoelectronic properties relevant for device applications. Here, the static and dynamic structures of linear alkylammonium and aromatic spacers in lead iodide RP phases (n = 1) are characterized at ambient temperatures using solid-state NMR (ssNMR) spectroscopy and compared with previously reported crystal structures derived from X-ray diffraction. Rigid and flexible sites of spacers are distinguished by examining 13C{1H} and 15N{1H} cross-polarization magic-angle spinning (CP-MAS) signal intensity build-up. Different trends in site-specific rigidity are observed for short and long alkylammonium spacers. Short spacers (e.g., butylammonium) are attached by strong affinity interactions to lead iodide octahedra, whereas longer spacers (e.g., dodecylammonium) are more rigid within the RP interlayer than near the octahedral surface. Phenethylammonium and butylammonium spacers are similarly rigid, and we estimate that the local reorientation time scale of phenyl rings is 10-100 μs by 2D 13C CP-variable contact (CP-VC) experiments. These ssNMR results indicate that the interplay between spacer interactions with lead iodide octahedra (Coulombic and hydrogen-bonding) and van der Waals forces between spacers is responsible for a variety of site-specific dynamics and local structural distortions at intermediate time scales (microsecond to millisecond). This study demonstrates a general method to characterize nanoscale structures and site-specific dynamics that contribute to structural and electronic disorder in functional optoelectronic RP phases.
Excitonic Properties of Chemically Synthesized 2D Organic–Inorganic Hybrid Perovskite Nanosheets
Zhang, Qi,Chu, Leiqiang,Zhou, Feng,Ji, Wei,Eda, Goki
, (2018/03/29)
2D organic–inorganic hybrid perovskites (OIHPs) represent a unique class of materials with a natural quantum-well structure and quasi-2D electronic properties. Here, a versatile direct solution-based synthesis of mono- and few-layer OIHP nanosheets and a systematic study of their electronic structure as a function of the number of monolayers by photoluminescence and absorption spectroscopy are reported. The monolayers of various OIHPs are found to exhibit high electronic quality as evidenced by high quantum yield and negligible Stokes shift. It is shown that the ground exciton peak blueshifts by ≈40 meV when the layer thickness reduces from bulk to monolayer. It is also shown that the exciton binding energy remains effectively unchanged for (C6H5(CH2)2NH3)2PbI4 with the number of layers. Similar trends are observed for (C4H9NH3)2PbI4 in contrast to the previous report. Further, the photoluminescence lifetime is found to decrease with the number of monolayers, indicating the dominant role of surface trap states in nonradiative recombination of the electron–hole pairs.
