Güvenç, Çetin MeriçToso, StefanoIvanov, Yurii P.Saleh, GabrieleBalcı, SinanDivitini, GiorgioManna, Liberato2025-02-052025-02-0520241936-08511936-086Xhttps://doi.org/10.1021/acsnano.4c14536https://hdl.handle.net/11147/15303Toso, Stefano/0000-0002-1621-5888; BALCI, SINAN/0000-0002-9809-8688; Guvenc, Cetin Meric/0000-0001-9197-5310We report the synthesis of ethylammonium lead iodide (EAPbI3) colloidal nanocrystals as another member of the lead halide perovskites family. The insertion of an unusually large A-cation (274 pm in diameter) in the perovskite structure, hitherto considered unlikely due to the unfavorable Goldschmidt tolerance factor, results in a significantly larger lattice parameter compared to the Cs-, methylammonium- and formamidinium-based lead halide perovskite homologues. As a consequence, EAPbI3 nanocrystals are highly unstable, evolving to a nonperovskite delta-EAPbI3 polymorph within 1 day. Also, EAPbI3 nanocrystals are very sensitive to electron irradiation and quickly degrade to PbI2 upon exposure to the electron beam, following a mechanism similar to that of other hybrid lead iodide perovskites (although degradation can be reduced by partially replacing the EA+ ions with Cs+ ions). Interestingly, in some cases during this degradation the formation of an epitaxial interface between (EA x Cs1-x )PbI3 and PbI2 is observed. The photoluminescence emission of the EAPbI3 perovskite nanocrystals, albeit being characterized by a low quantum yield (similar to 1%), can be tuned in the 664-690 nm range by regulating their size during the synthesis. The emission efficiency can be improved upon partial alloying at the A site with Cs+ or formamidinium cations. Furthermore, the morphology of the EAPbI3 nanocrystals can be chosen to be either nanocube or nanoplatelet, depending on the synthesis conditions.eninfo:eu-repo/semantics/openAccessPerovskitesNanocrystalsEthylammoniumNanoplateletsPhase TransformationsHeterostructuresArticle2-s2.0-8521340944910.1021/acsnano.4c14536