Structural and thermodynamic limits of layer thickness in 2D halide perovskites
In the fast-evolving field of halide perovskite semiconductors, the 2D perovskites (A′) 2 (A) n −1 M n X 3 n +1 [where A = Cs + , CH 3 NH 3 + , HC(NH 2 ) 2 + ; A′ = ammonium cation acting as spacer; M = Ge 2+ , Sn 2+ , Pb 2+ ; and X = Cl − , Br − , I − ] have recently made a critical entry. The n value defines the thickness of the 2D layers, which controls the optical and electronic properties. The 2D perovskites have demonstrated preliminary optoelectronic device lifetime superior to their 3D counterparts. They have also attracted fundamental interest as solution-processed quantum wells with structural and physical properties tunable via chemical composition, notably by the n value defining the perovskite layer thickness. The higher members ( n > 5) have not been documented, and there are important scientific questions underlying fundamental limits for n . To develop and utilize these materials in technology, it is imperative to understand their thermodynamic stability, fundamental synthetic limitations, and the derived structure–function relationships. We report the effective synthesis of the highest iodide n -members yet, namely (CH 3 (CH 2 ) 2 NH 3 ) 2 (CH 3 NH 3 ) 5 Pb 6 I 19 ( n = 6) and (CH 3 (CH 2 ) 2 NH 3 ) 2 (CH 3 NH 3 ) 6 Pb 7 I 22 ( n = 7), and confirm the crystal structure with single-crystal X-ray diffraction, and provide indirect evidence for “(CH 3 (CH 2 ) 2 NH 3 ) 2 (CH 3 NH 3 ) 8 Pb 9 I 28 ” (“ n = 9”). Direct HCl solution calorimetric measurements show the compounds with n > 7 have unfavorable enthalpies of formation (Δ H f ), suggesting the formation of higher homologs to be challenging. Finally, we report preliminary n -dependent solar cell efficiency in the range of 9–12.6% in these higher n -members, highlighting the strong promise of these materials for high-performance devices.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States); Energy Frontier Research Centers (EFRC) (United States). Center for Light Energy Activated Redox Processes (LEAP); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Northwestern Univ., Evanston, IL (United States); Univ. of California, Davis, CA (United States)
- Sponsoring Organization:
- US Department of the Navy, Office of Naval Research (ONR); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Grant/Contract Number:
- 89233218CNA000001; AC02-06CH11357; FG02-03ER46053; SC0001059
- OSTI ID:
- 1487311
- Alternate ID(s):
- OSTI ID: 1766992
OSTI ID: 1566665
OSTI ID: 1576006
- Report Number(s):
- LA-UR--19-20438
- Journal Information:
- Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 1 Vol. 116; ISSN 0027-8424
- Publisher:
- National Academy of SciencesCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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