Hybrid halide perovskites consisting of corner-sharing metal halide octahedra and small cuboctahedral cages filled with counter cations have proven to be prominent candidates for many high-performance optoelectronic devices. The stability limits of their three-dimensional perovskite framework are defined by the size range of the cations present in the cages of the structure. In some cases, the stability of the perovskite-type structure can be extended even when the counterions violate the size and shape requirements, as is the case in the so-called "hollow"perovskites. In this work, we engineered a new family of 3D highly defective yet crystalline "hollow"bromide perovskites with general formula (FA)1-x(en)x(Pb)1-0.7x(Br)3-0.4x (FA = formamidinium (FA+), en = ethylenediammonium (en2+), x = 0-0.44). Pair distribution function analysis shed light on the local structural coherence, revealing a wide distribution of Pb-Pb distances in the crystal structure as a consequence of the Pb/Br-deficient nature and en inclusion in the lattice. By manipulating the number of Pb/Br vacancies, we finely tune the optical properties of the pristine FAPbBr3 by blue shifting the band gap from 2.20 to 2.60 eV for the x = 0.42 en sample. A most unexpected outcome was that at x> 0.33 en incorporation, the material exhibits strong broad light emission (1% photoluminescence quantum yield (PLQY)) that is maintained after exposure to air for more than a year. This is the first example of strong broad light emission from a 3D hybrid halide perovskite, demonstrating that meticulous defect engineering is an excellent tool for customizing the optical properties of these semiconductors.
Bibliographical noteFunding Information:
This work was primarily supported by the Department of Energy, Office of Science, Basic Energy Sciences, under Grant No. SC0012541 (sample synthesis and structure and property characterization). Photoluminescence measurements were supported by the National Science Foundation (NSF) Materials Research Science and Engineering Center (MRSEC) at Northwestern University (NSF DMR-1720139). This work made use of the SPID and EPIC facilities of Northwestern University’s NU ANCE Center as well as the IMSERC facilities, which have received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the MRSEC program (NSF DMR-1720139) at the Materials Research Center, the State of Illinois, and the International Institute for Nanotechnology (IIN). This work was performed, in part, at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, and supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. The MRL Shared Experimental Facilities are supported by the MRSEC Program of the NSF under Award No. DMR 1720256, a member of the NSF-funded Materials Research Facilities Network. G.N.M.R. acknowledges financial support from EU H2020 (795091) and IR-RMN-THC FR-3050 CNRS for conducting ssNMR measurements. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility, operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
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