Characterization of the Valence and Conduction Band Levels of n = 1 2D Perovskites: A Combined Experimental and Theoretical Investigation,Advanced Energy Materials

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Characterization of the Valence and Conduction Band Levels of n = 1 2D Perovskites: A Combined Experimental and Theoretical Investigation
Advanced Energy Materials ( IF 24.4 ) Pub Date : 2018-02-13 , DOI: 10.1002/aenm.201703468
Scott Silver ₁ , Jun Yin ₂ , Hong Li ₃ , Jean-Luc Brédas ₃ , Antoine Kahn ₁

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This study presents a combined experimental and theoretical study of the electronic structure of two 2D metal halide perovskite films. Ultraviolet and inverse photoemission spectroscopies are performed on solution‐processed thin films of the n = 1 layered perovskite butylammonium lead iodide and bromide, BA₂PbI₄ and BA₂PbBr₄, characterized by optical absorption and X‐ray diffraction, to determine their valence and conduction band densities of states, transport gaps, and exciton binding energies. The electron spectroscopy results are compared with the densities of states determined by density functional theory calculations. The remarkable agreement between experiment and calculation enables a detailed identification and analysis of the organic and inorganic contributions to the valence and conduction bands of these two hybrid perovskites. The electron affinity and ionization energies are found to be 3.1 and 5.8 eV for BA₂PbI₄, and 3.1 and 6.5 eV for BA₂PbBr₄. The exciton binding energies are estimated to be 260 and 300 meV for the two materials, respectively. The 2D lead iodide and bromide perovskites exhibit significantly less band dispersion and a larger density of states at the band edges than the 3D analogs. The effects of using various organic ligands are also discussed.

中文翻译：

n = 1 2D钙钛矿的价态和导带能级的表征：组合的实验和理论研究

这项研究提供了两个二维金属卤化物钙钛矿薄膜的电子结构的组合实验和理论研究。紫外线和逆光电发射光谱是在溶液处理的薄的膜进行Ñ = 1层状钙钛矿丁基碘化铅和溴化，BA ₂碘化铅₄和BA ₂ PbBr ₄以光吸收和X射线衍射为特征，以确定它们的价态和态，传输带隙和激子结合能的能带密度。将电子光谱结果与通过密度泛函理论计算确定的状态密度进行比较。实验和计算之间的显着一致性使得能够详细鉴定和分析有机和无机对这两种杂化钙钛矿的价带和导带的贡献。电子亲和力和电离能被发现是3.1和5.8电子伏特为BA ₂碘化铅₄，和3.1和6.5电子伏特为BA ₂ PbBr ₄。两种材料的激子结合能估计分别为260和300 meV。与3D类似物相比，2D碘化铅和溴化钙钛矿的能带分散性低得多，能带边缘处的态密度更大。还讨论了使用各种有机配体的效果。

更新日期：2018-02-13

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