Spotlights Cite This: J. Phys. Chem. Lett. 2018, 9, 677−677
pubs.acs.org/JPCL
Spotlights: Volume 9, Issue 3
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ENHANCED THERMAL STABILITY IN PEROVSKITE SOLAR CELLS BY ASSEMBLING 2D/3D STACKING STRUCTURES What does the killer bee have in common with the arguably more charming goldendoodle? Both resulted from crossbreeding for the purpose of combining positive attributes of two different creatures. Sometimes hybridization is a raging success and provides you with a loyal companion, and sometimes it is a failure that leads to widespread (though mostly unnecessary) panic. In the field of photovoltaics, the combination of two-dimensional (2D) and three-dimensional (3D) perovskites may not provide you with a new family pet, but its impact may prove to be even more important to the future of the planet. Hybrid organic−inorganic halide perovskites are already known as promising materials in such optoelectronic fields as solar cells, light-emitting diodes, and photodetectors because of their outstanding optoelectronic properties. Much work has been done to compare 2D perovskites with their 3D counterparts, and each appears to have its own advantages: 2D perovskites show more stability, whereas 3D perovskites achieve a much higher power conversion efficiency. Combining the two perovskites could lead to solar cells that are both stable and highly efficient. Lin et al. (10.1021/acs.jpclett.7b02679) report a strategy to construct 2D/3D stacking structures in perovskite solar cells for enhanced stability and efficiency by converting only the top surface of 3D perovskites into 2D materials. They propose a method of forming 2D/3D stacking structures via the reaction of 3D perovskites with n-Butylamine (BA). BA treatment results in a smooth 2D perovskite layer on 3D perovskites with good coverage. The authors found that the resulting photovoltaic devices with 2D/3D stacking structures showed much better stability than their 3D counterparts when subjected to heat stress tests. They also report that the conversion of defective surfaces into 2D layers induced passivation of the 3D perovskites, resulting in enhanced efficiency.
breaking the π-conjugation and/or decreasing the dispersion of the electronic bands near the Fermi level. They demonstrate that the presence of defects can open a small gap, consistent with the experimentally inferred hopping barrier. These types of defects are shown to be interrelated: a strike−slip fault leads to the presence of a layer−layer displacement defect. The authors conclude that, although extended conjugated sheets of Ni3(HITP)2 are highly conducting and the ideal pristine material has a metallic electronic structure, the overall conductivity is governed by charge hopping within the microstructure because of the presence of defects such as grain boundaries and nonoptimal layer−layer displacements. The findings demonstrate the importance of considering the microstructure in these types of materials, in addition to the bulk electronic structure, for reliable modeling of electronic properties. The results also highlight the need for greater control over the microstructure of these materials so that consistent and predictable electronic properties can be achieved.
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UNRAVELING THE SEMICONDUCTING/METALLIC DISCREPANCY IN NI3(HITP)2 As any good chemist knows, theory and experiment are two sides of the same coin, but heads and tails often look very different. For example, experiments with Ni3(2,3,6,7,10,11hexaiminotriphenylene)2 (Ni3(HITP)2), a π-stacked layered metal−organic framework material analogous to graphene, indicate that it is semiconducting, but theoretical studies predict it to be metallic. Foster et al. (10.1021/acs.jpclett.7b03140) studied the electronic structure of Ni3(HITP)2 with larger structural defects, and they found that defects can change the electronic nature of the material. Because previous experimental work was done on specimens containing complex nanocrystalline microstructures, and because internal interfaces tend to introduce transport barriers, the authors used density functional theory to investigate the influence of internal interface defects on the electronic structure of Ni3(HITP)2. Their findings show that interface defects can introduce a transport barrier by © 2018 American Chemical Society
Published: February 1, 2018 677
DOI: 10.1021/acs.jpclett.8b00239 J. Phys. Chem. Lett. 2018, 9, 677−677
