Ruddlesden-Popper Hybrid Lead Iodide Perovskite 2D Homologous Semiconductors
Ruddlesden-Popper Hybrid Lead Iodide Perovskite 2D Homologous Semiconductors
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DOI：
10.1021/acs.chemmater.6b00847
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发表时间：
2016-04-26
影响因子：
8.6
通讯作者：
Kanatzidis, Mercouri G.
中科院分区：
文献类型：
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作者：
Stoumpos, Constantinos C.;Cao, Duyen H.;Kanatzidis, Mercouri G.
杂化的二维卤化物钙钛矿材料最近引起了人们的极大兴趣，因为它们可以作为钙钛矿太阳能电池的优良光吸收材料。本文介绍了2D(CH3(CH2)(3)NH3)(2)(CH3NR3)(n-1)PbnI3n+1(n=1，2，3，4，无穷大)钙钛矿的大规模合成、晶体结构和光学性质。这些材料由定义明确的无机钙钛矿层与笨重的丁基铵阳离子插层组成，这些阳离子充当这些碎片之间的间隔物，采用Ruddlesden-Popper类型的晶体结构。我们发现，通过调节间隔阳离子与有机小阳离子之间的比例可以综合控制钙钛矿厚度(N)，从而实现了化合物的高纯度和大范围的分离。(CH3(CH2)(3)NH3)(2)(CH3NH3)-Pb2I7(n=2，Cc2m；a=8.9470(4)，b=39.347(2)angstrom，c=8.8589(6))，(CH3(CH2)(3)NH3)(2)(CH3NH3)(2)Pb3I10(n=3，C2cb；A=8.9275(6)，b=51.959(4)埃，c=8.8777(6))和(CH_3(CH_2)(3)NH_3)(2)(CH_3NH_3)(3)Pb_4I_(13)(n=4，Cc_2m；a=8.9274(4)，b=64.383(4)埃，c=8.8816(4))。化合物的非线性光学性质的测量和密度泛函理论(DFT)的计算支持这些化合物是非中心对称的。该系列的带隙从2.43 eV(n=1)到1.50 eV(n=无穷大)逐渐变化，中间值分别为2.17 eV(n=2)、2.03 eV(n=3)和1.91 eV(n=4)。密度泛函理论计算证实了这一实验趋势，并预测了Ruddlesden Popper系列所有成员的直接带隙。对于空穴和电子，估算的有效质量分别为m(H)=0.14m(0)和m(E)=0.08m(0)，并且发现它们几乎与组成无关。较高n元的带隙表明，这些化合物可以作为太阳能电池的高效吸光剂，具有更好的溶液加工性和良好的环境稳定性。这些化合物在室温下表现出强烈的光致发光，发射波长分别为2.35 eV(n=1)、2.12 eV(n=2)、2.01 eV(n=3)和1.90 eV(n=4)，表明它们在发光二极管中具有潜在的应用前景。此外，由于有机间隔层和无机钙钛矿层之间的低维和介电性质的差异，这些化合物自然地存在多量子阱结构，从而在室温下产生稳定的激子。
The hybrid two-dimensional (2D) halide perovskites have recently drawn significant interest because they can serve as excellent photoabsorbers in perovskite solar cells. Here we present the large scale synthesis, crystal structure, and optical characterization of the 2D (CH3(CH2)(3)NH3)(2)(CH3NR3)(n-1)PbnI3n+1 (n = 1, 2, 3, 4, infinity) perovskites, a family of layered compounds with tunable semiconductor characteristics. These materials consist of well-defined inorganic perovskite layers intercalated with bulky butylammonium cations that act as spacers between these fragments, adopting the crystal structure of the Ruddlesden-Popper type. We find that the perovskite thickness (n) can be synthetically controlled by adjusting the ratio between the spacer cation and the small organic cation, thus allowing the isolation of compounds in pure form and large scale. The orthorhombic crystal structures of (CH3(CH2)(3)NH3)(2)(CH3NH3)-Pb2I7 (n = 2, Cc2m; a = 8.9470(4), b = 39.347(2) angstrom, c = 8.8589(6)), (CH3(CH2)(3)NH3)(2)(CH3NH3)(2)Pb3I10 (n = 3, C2cb; a = 8.9275(6), b = 51.959(4) angstrom, c = 8.8777(6)), and (CH3(CH2)(3)NH3)(2)(CH3NH3)(3)Pb4I13 (n = 4, Cc2m; a = 8.9274(4), b = 64.383(4) angstrom, c = 8.8816(4)) have been solved by single-crystal X-ray diffraction and are reported here for the first time. The compounds are noncentrosymmetric, as supported by measurements of the nonlinear optical properties of the compounds and density functional theory (DFT) calculations. The band gaps of the series change progressively between 2.43 eV for the n = 1 member to 1.50 eV for the n = infinity adopting intermediate values of 2.17 eV (n = 2), 2.03 eV (n = 3), and 1.91 eV (n = 4) for those between the two compositional extrema. DFT calculations confirm this experimental trend and predict a direct band gap for all the members of the Ruddlesden Popper series. The estimated effective masses have values of m(h) = 0.14 m(0) and m(e) = 0.08 m(0) for holes and electrons, respectively, and are found to be nearly composition independent. The band gaps of higher n members indicate that these compounds can be used as efficient light absorbers in solar cells, which offer better solution processability and good environmental stability. The compounds exhibit intense room-temperature photoluminescence with emission wavelengths consistent with their energy gaps, 2.35 eV (n = 1), 2.12 eV (n = 2), 2.01 eV (n = 3), and 1.90 eV (n = 4) and point to their potential use in light-emitting diodes. In addition, owing to the low dimensionality and the difference in dielectric properties between the organic spacers and the inorganic perovskite layers, these compounds are naturally occurring multiple quantum well structures, which give rise to stable excitons at room temperature.