二维杂化金属-卤化物钙钛矿中的电荷-载流子动力学,Nano Letters

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二维杂化金属-卤化物钙钛矿中的电荷-载流子动力学
Nano Letters ( IF 9.6 ) Pub Date : 2016-10-06 00:00:00 , DOI: 10.1021/acs.nanolett.6b03114
Rebecca L. Milot ₁ , Rebecca J. Sutton ₁ , Giles E. Eperon ₁ , Amir Abbas Haghighirad ₁ , Josue Martinez Hardigree ₁ , Laura Miranda ₂ , Henry J. Snaith ₁ , Michael B. Johnston ₁ , Laura M. Herz ₁

Affiliation

杂化金属卤化物钙钛矿是有望用于太阳能电池的新材料。然而，它们在湿气存在下的化学稳定性仍然是一个明显的缺点。结合了疏水性有机中间层的准二维（2D）钙钛矿提供了更好的抵抗水分降解的能力，目前仍以整体电池效率为代价。为了阐明影响这些材料的光电性能的因素，我们研究了混合甲基铵（MA）-苯基乙基铵（PEA）碘化铅薄膜的电荷传输性能和晶体学取向，其与MA / PEA比率的关系；并且因此，“封装”的MA卤化铅层的厚度。我们发现，单分子电荷-载流子重组率首先随着PEA分数的增加而降低，极有可能是陷阱钝化的结果，但随着激子效应开始占主导地位，对于薄薄的约束层，其作用显着增加。发现双分子和俄歇复合速率常数对电子约束的变化敏感，这会改变电子跃迁的态密度。我们证明有效的载流子迁移率仍然非常高（近10厘米² V ^-1 s ^-1）用于中等PEA含量，并增强了导电性碘化铅层沿探测电场的优先取向。陷阱减少，电子限制和层取向之间的权衡导致中间PEA含量（50％）的计算得出的载流子扩散长度最大达到2.5μm。

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Charge-Carrier Dynamics in 2D Hybrid Metal–Halide Perovskites

Hybrid metal–halide perovskites are promising new materials for use in solar cells; however, their chemical stability in the presence of moisture remains a significant drawback. Quasi two-dimensional (2D) perovskites that incorporate hydrophobic organic interlayers offer improved resistance to degradation by moisture, currently still at the cost of overall cell efficiency. To elucidate the factors affecting the optoelectronic properties of these materials, we have investigated the charge transport properties and crystallographic orientation of mixed methylammonium (MA)–phenylethylammonium (PEA) lead iodide thin films as a function of the MA-to-PEA ratio and, thus, the thickness of the “encapsulated” MA lead–halide layers. We find that monomolecular charge-carrier recombination rates first decrease with increasing PEA fraction, most likely as a result of trap passivation, but then increase significantly as excitonic effects begin to dominate for thin confined layers. Bimolecular and Auger recombination rate constants are found to be sensitive to changes in electronic confinement, which alters the density of states for electronic transitions. We demonstrate that effective charge-carrier mobilities remain remarkably high (near 10 cm²V⁻¹s⁻¹) for intermediate PEA content and are enhanced for preferential orientation of the conducting lead iodide layers along the probing electric field. The trade-off between trap reduction, electronic confinement, and layer orientation leads to calculated charge-carrier diffusion lengths reaching a maximum of 2.5 μm for intermediate PEA content (50%).

更新日期：2016-10-06

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