Mechanistic Insights into Excitonic Photoluminescence in Hybrid Organic-Inorganic Perovskites with Targeted Regulation of Organic Cations
We report a mech-anistic study of ex-citonic photolumi-nescence in pre-designed hybrid organic-inorganic perovskite(HOIP)systems,i.e.,(DMAEA)Pb2I6,(DMAPA)PbI4,(DEAEA)Pb2I6,and(DEAPA)4Pb5I18,featuring targeted regulation of organic cations.Starting from the prototype DMAEA(i.e.,2-N,N-dimethylamino-1-ethylamine)for(DMAEA)Pb2I6,the other three HOIPs differ only in the extensions with CH2 group(s)at the"head"or/and"tail"of DMAEA that is an"alkylated ammonia".Their crystal structures are constructed and structural distortions are evaluated.The steady-state/transient absorption and emission spectroscopic characterizations,combined with the band-structure calculations,are conducted.The two different photoluminescence(PL)mechanisms are identified,i.e.,PL emissions dominated by free excitons for(DMAPA)PbI4 and by self-trapped excitons for(DMAEA)Pb2I6,(DEAEA)Pb2I6,and(DEAPA)4Pb5I18.The self-trapped excitonic effect in-volved in the latter three HOIPs is quantitatively analyzed.This work would be of guiding value for the design of HOIP systems based on organic-cation engineering,beneficial for the pertinent performance optimization in light-emitting applications.
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