Zhang Yao, Zhu Leilei, Yang Zhaoxia, Tao Weijian, Chen Zeng, Li Tianjing, Lei Haixin, Li Congzhou, Wang Lin, Tian Wenming, Li Zhenyu, Shang Honghui, Zhu Haiming
State Key Laboratory of Modern Optical Instrument, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China.
ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou, Zhejiang 311200, China.
J Am Chem Soc. 2024 Mar 20;146(11):7831-7838. doi: 10.1021/jacs.4c01115. Epub 2024 Mar 6.
Low-dimensional lead halide perovskites with broadband emission hold great promise for single-component white-light-emitting (WLE) devices. The origin of their broadband emission has been commonly attributed to self-trapped excitons (STEs) composed of localized electronic polarization with a distorted lattice. Unfortunately, the exact electronic and structural nature of the STE species in these WLE materials remains elusive, hindering the rational design of high-efficiency WLE materials. In this study, by combining ultrafast transient absorption spectroscopy and calculations, we uncover surprisingly similar STE features in two prototypical low dimensional WLE perovskite single crystals: 1D (DMEDA)PbBr and 2D (EDBE)PbBr, despite of their different dimensionalities. Photoexcited excitons rapidly localize to intrinsic STEs within ∼250 fs, contributing to the white light emission. Crucially, STEs in both systems exhibit characteristic absorption features akin to those of Pb and Pb. Further atomic level theoretical simulations confirm photoexcited electrons and holes are localized on the Pb site to form Pb- and Pb-like species, resembling transient photoinduced Pb disproportionation. This study provides conclusive evidence on the key excited state species for exciton self-trapping and broadband emission in low dimensional lead halide WLE perovskites and paves the way for the rational design of high-efficiency WLE materials.
具有宽带发射的低维铅卤化物钙钛矿在单组分白光发射（WLE）器件方面具有巨大潜力。其宽带发射的起源通常归因于由晶格畸变的局域电子极化组成的自陷激子（STE）。不幸的是，这些WLE材料中STE物种的确切电子和结构性质仍然难以捉摸，这阻碍了高效WLE材料的合理设计。在本研究中，通过结合超快瞬态吸收光谱和计算，我们在两种典型的低维WLE钙钛矿单晶：一维（DMEDA）PbBr和二维（EDBE）PbBr中发现了惊人相似的STE特征，尽管它们的维度不同。光激发激子在约250飞秒内迅速局域化为本征STE，这有助于白光发射。至关重要的是，两个系统中的STE都表现出类似于Pb和Pb的特征吸收特征。进一步的原子水平理论模拟证实，光激发电子和空穴局域在Pb位点上，形成类似Pb和Pb的物种，类似于瞬态光致Pb歧化。这项研究为低维铅卤化物WLE钙钛矿中激子自陷和宽带发射的关键激发态物种提供了确凿证据，并为高效WLE材料的合理设计铺平了道路。
