NSRRC Activity Report 2022

032 NSRRC ACTIVITY REPORT 2022 developed high-entropy perovskite (HEP) nanocrystals (NCs) that exhibited excellent colloidal stability with narrowband emission and employed X-ray scattering for crystallographic analysis at TPS 13A . Their team discovered that the precursor metal bromides of colloidal perovskite could be doped with several metal ions (Mg 2+ , Zn 2+ , and Cd 2+ ) at the B-site of the perovskite structure. Notably, when alloying was performed, photoluminescence (PL) quantum yield (η PL ) increased from 75% to up to 95%, and the clear PL blueshifts that occurred are attributable to lattice contraction. In addition, when the number of secondary elements involved increased, the average PL lifetime (τ avg ) decreased from 27.3 ns to as low as 4.6 ns. To identify the factors that facilitate the enhancement of the optical properties of HEP NCs, the aforementioned team employed synchronized X-ray scattering at TPS 13A to interpret the lattice of perovskite crystal structures. The team discovered that when a higher number of secondary elements were involved, components with a higher degree of wavenumber shifts were obtained. For example, for MA(PbMgZnCd)Br 3 HEP NCs, components centered at q = 10.10 and 11.07 nm −1 , which corresponded to the d-spacings of 6.22 and 5.67 Å, respectively, were resolved, or approximately 5.0% expansion and 4.5% contraction with multicomponent Lorentzians were achieved by magnifying the (100) plane peaks extracted from grazing-incidence wide-angle X-ray scattering (GIWAXS) patterns. Furthermore, the results indicated that high-entropy alloying reduced the lead content in the alloy by approximately 55%, which could be an advantage for promoting the further commercialization of MHPs. In summary, the team of Shih and Chiu synthesized a noteworthy class of lead-reduced perovskite NCs, namely HEP NCs. With a lead reduction of up to 55%, the prepared HEP NCs exhibited excellent optical properties and colloidal stability. Crystallographic analysis revealed that the formation of interstitial and doping phases upon high- entropy alloying was responsible for the stabilization of the lead-reduced perovskite lattices in the prepared HEP NCs. (Reported by Yu-Cheng Chiu, National Taiwan University of Science and Technology) This report features the work of Yu-Cheng Chiu and Chih-Jen Shih, and their co-workers published in ACS Nano 10 , 9720 (2016) and J. Am. Chem. Soc. 144 , 5864 (2022). TPS 13A Biological Small-angle X-ray Scattering • GIWAXS • Biology, Materials Science, Physics, Chemistry References 1. S. Kumar, J. Jagielski, Y. Sergii, P. Rice, Y. C. Chiu, M. Wang, G. Nedelcu, Y. Kim, S. Lin, E. J. G. Santos, M. V. Kovalenko, C. J. Shih, ACS Nano 10 , 9720 (2016). 2. S. Solari, L.-N. Poon, M. Wörle, F. Krumeich, Li, Y. T. Li, Y. C. Chiu, C. J. Shih, J. Am. Chem. Soc. 144 , 5864 (2022).