Single Ensemble Nonexponential Photoluminescent Population Decays from a Broadband White-Light-Emitting Perovskite,Journal of the American Chemical Society

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Single Ensemble Nonexponential Photoluminescent Population Decays from a Broadband White-Light-Emitting Perovskite
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-09-10 , DOI: 10.1021/jacs.0c05636
Joseph E Thomaz ₁ , Kurt P Lindquist ₁ , Hemamala I Karunadasa _{1,

2} , Michael D Fayer ₁

Affiliation

The mechanism of white-light emission from layered Pb-X (X = Cl or Br) perovskites following UV excitation has generated considerable interest. Prior time-dependent studies indicated that the broadband photoluminescence (PL) from (110) perovskites arises from a distribution of self-trapped excitonic sites emitting in different regions of the visible spectrum with different decay dynamics. Here, using time-correlated single photon counting to study single crystals, we show that a single ensemble of excited states gives rise to the white-light emission from the (110) perovskite (EDBE)PbBr4 (EDBE = 2,2'-(ethylenedioxy)-bis-(ethylammonium)). We identified a localized defect region of the crystal that adds a distinct emissive band. The decay dynamics of this emission was previously included in the PL decay of the broad emission. Following the decay of a rapidly relaxing (0.6 ns) spectral side band, the broad emission line shape is constant to 100 ns. Although the emission originates from a single excited state, the luminescent decay is tri-exponential with time constants 1.20 ns, 8.48 ns, and 21.75 ns. Two heuristic models for the tri-exponential decay involving defects are discussed. Experiments on spin-coated films of (EDBE)PbBr4 show a faster non-exponential luminescence decay in which the slowest component of the crystal PL is absent. Like the crystals, the PL occurs from a single ensemble after the fast relaxation of the side band. The results demonstrate that the broadband emission of (EDBE)PbBr4 single crystals and spin-coated films arises from a single ensemble and not from a set of distinct excited states with different emission wavelengths and lifetimes.

中文翻译：

来自宽带白光发光钙钛矿的单一集合非指数光致发光种群衰减

紫外激发后层状 Pb-X（X = Cl 或 Br）钙钛矿的白光发射机制引起了人们极大的兴趣。先前的时间相关研究表明，（110）钙钛矿的宽带光致发光（PL）源于在可见光谱的不同区域以不同衰减动力学发射的自陷激子位点的分布。在这里，使用与时间相关的单光子计数来研究单晶，我们表明单个激发态集合会引起（110）钙钛矿（EDBE）PbBr4（EDBE = 2,2'-（乙二氧基)-双-(乙基铵))。我们确定了晶体的局部缺陷区域，它增加了一个独特的发射带。这种发射的衰减动力学先前包含在宽发射的 PL 衰减中。在快速弛豫 (0.6 ns) 光谱边带衰减之后，宽发射线形状恒定为 100 ns。尽管发射源自单个激发态，但发光衰减是三指数的，时间常数为 1.20 ns、8.48 ns 和 21.75 ns。讨论了涉及缺陷的三指数衰减的两种启发式模型。(EDBE)PbBr4 旋涂薄膜的实验显示出更快的非指数发光衰减，其中晶体 PL 的最慢成分不存在。与晶体一样，PL 发生在边带快速弛豫后的单个系综中。结果表明，(EDBE)PbBr4 单晶和旋涂膜的宽带发射来自单个系综，而不是来自一组具有不同发射波长和寿命的不同激发态。

更新日期：2020-09-10

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