Goldschmidt's Rules and Strontium Replacement in Lead Halogen Perovskite Solar Cells: Theory and Preliminary Experiments on CH3NH3SrI3
Goldschmidt's Rules and Strontium Replacement in Lead Halogen Perovskite Solar Cells: Theory and Preliminary Experiments on CH3NH3SrI3
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DOI：
10.1021/acs.jpcc.5b06436
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发表时间：
2015-11-19
影响因子：
3.7
通讯作者：
Edvinsson, Tomas
中科院分区：
文献类型：
--
作者：
Jacobsson, T. Jesper;Pazoki, Meysam;Edvinsson, Tomas
在过去的几年中，有机铅卤钙钛矿已经成为一类非常有前途的太阳能电池材料，认证的太阳能电池效率现在超过20%。然而，人们对基于水溶性铅化合物的新太阳能电池技术可能带来的环境和法律问题表示担忧。因此，用毒性较小的元素取代钙钛矿结构中的铅，而不降低有利的光物理性能，将是令人感兴趣的。在本文中，取代铅与其他金属离子的可能性进行了探索，通过以下的置换规则的Goldschmidt与额外的量子力学的考虑。该分析提供了一个替代铅的概念工具箱，以及对金属卤素钙钛矿的光物理学的额外见解。这种方法的例子是特别关注无毒且相对便宜的锶。Sr 2+和Pb 2+的离子半径几乎相同，表明可以进行交换而不影响晶体结构。对金属离子和它们的卤素盐的耦合簇计算给出的键合模式是足够相似的和密度泛函理论（DFT）揭示的锶钙钛矿，CH3NH3SrI3，是一个稳定的相，尽管铅和锶之间的电负性的差异。这进一步得到二元PM和SrI2化合物的存在以及锶钙钛矿的有益形成能的支持。电子性质的CH 3NH3SrI3和CH 3NH3PbI3的模拟和比较，揭示了较高程度的离子相互作用的金属卤素结合在锶钙钛矿。这是锶的较低电负性的结果，其与Sr 2+的价态中缺乏d轨道一起导致较高的带隙。锶钙钛矿的带隙估计为3.6eV，不幸的是，这对于有效的光吸收剂来说太高了。使用湿化学方法对锶钙钛矿的实验合成的初步研究显示，它比铅钙钛矿更难生产。这被解释为：金属碘盐中不同的键合模式的结果，其阻碍了用于形成钙钛矿的甲基铵插层途径。相反，气相法被认为是更有前途的合成路线。
During the past few years, organic lead halogen perovskites have emerged as a class of highly promising solar cell materials, with certified solar cell efficiencies now surpassing 20%. Concerns have, however, been raised about the possible environmental and legalization problems associated with a new solar cell technology based on a water-soluble lead compound. Replacing lead in the perovskite structure: with a less toxic element, without degrading the favorable photo physical properties, would therefore be of interest. In this paper, the possibility of replacing lead with other metal ions is explored by following the replacement rules of Goldschmidt together with additional quantum mechanical considerations. This analysis provides a conceptual toolbox toward replacing lead, as well as additional insights into the photo physics of the metal halogen perovskites. This approach is exemplified by focusing on strontium in particular, which is nontoxic and relatively inexpensive. The ionic radius of Sr2+ and Pb2+ are almost identical, suggesting an exchange could be made without affecting the crystal structure. Couple cluster calculations on the metal ions and their halogen salts give the bonding patterns to be sufficiently similar and density functional theory (DFT) revealed the strontium perovskite, CH3NH3SrI3, to be a stable phase, despite the difference in electronegativity between lead and strontium. This is further supported by the existence of binary PM, and SrI2 compounds and the beneficial formation energy of the strontium perovskite. The electronic properties of both CH3NH3SrI3 and CH3NH3PbI3 were simulated and compared, revealing a higher degree of ionic interaction in the metal halogen bound in the strontium perovskite. This is a consequence of the lower electronegativity of strontium, which, together with the lack of d-orbitals in the Valence of Sr2+, results, in a higher band gap. The band gap for the strontium perovskite was estimated to 3.6 eV, which unfortunately is too high for an efficient photo absorber. Initial investigations on experimental synthesis of the strontium perovskite, using wet chemical methods, revealed it to be harder to produce than the lead perovskite This is explained as a:consequence of different bonding patterns in the metal iodine salts, which obstruct the methylammonium intercalation pathway utilized for forming the perovskite. Vapor phase methods are instead suggested as more promising synthesis routes.