Jana Manoj K, Janke Svenja M, Dirkes David J, Dovletgeldi Seyitliyev, Liu Chi, Qin Xixi, Gundogdu Kenan, You Wei, Blum Volker, Mitzi David B
Department of Mechanical Engineering and Materials Science , Duke University , Durham , North Carolina 27708 , United States.
Department of Chemistry , Duke University , Durham , North Carolina 27708 , United States.
J Am Chem Soc. 2019 May 15;141(19):7955-7964. doi: 10.1021/jacs.9b02909. Epub 2019 May 7.
Three-dimensional (3D) hybrid organic-inorganic lead halide perovskites (HOIPs) feature remarkable optoelectronic properties for solar energy conversion but suffer from long-standing issues of environmental stability and lead toxicity. Associated two-dimensional (2D) analogues are garnering increasing interest due to superior chemical stability, structural diversity, and broader property tunability. Toward lead-free 2D HOIPs, double perovskites (DPs) with mixed-valent dual metals are attractive. Translation of mixed-metal DPs to iodides, with their prospectively lower bandgaps, represents an important target for semiconducting halide perovskites, but has so far proven inaccessible using traditional spacer cations due to either intrinsic instability or formation of competing non-perovskite phases. Here, we demonstrate the first example of a 2D Ag-Bi iodide DP with a direct bandgap of 2.00(2) eV, templated by a layer of bifunctionalized oligothiophene cations, i.e., (bis-aminoethyl)bithiophene, through a collective influence of aromatic interactions, hydrogen bonding, bidentate tethering, and structural rigidity. Hybrid density functional theory calculations for the new material reveal a direct bandgap, consistent with the experimental value, and relatively flat band edges derived principally from Ag-d/I-p (valence band) and Bi-p/I-p (conduction band) states. This work opens up new avenues for exploring specifically designed organic cations to stabilize otherwise inaccessible 2D HOIPs with potential applications for optoelectronics.
三维（3D）有机-无机杂化铅卤化物钙钛矿（HOIPs）具有卓越的光电性能，可用于太阳能转换，但长期存在环境稳定性和铅毒性问题。相关的二维（2D）类似物因其优异的化学稳定性、结构多样性和更广泛的性能可调性而越来越受到关注。对于无铅二维HOIPs，具有混合价态双金属的双钙钛矿（DPs）很有吸引力。将混合金属DPs转化为碘化物，其带隙可能更低，这是半导体卤化物钙钛矿的一个重要目标，但由于内在不稳定性或形成竞争性非钙钛矿相，迄今为止使用传统间隔阳离子已证明无法实现。在此，我们展示了第一个二维Ag-Bi碘化物DP的例子，其直接带隙为2.00(2) eV，由一层双功能化的寡聚噻吩阳离子，即（双氨基乙基）联噻吩模板化，通过芳香相互作用、氢键、双齿连接和结构刚性的共同影响。对新材料的杂化密度泛函理论计算揭示了与实验值一致的直接带隙，以及主要由Ag-d/I-p（价带）和Bi-p/I-p（导带）态产生的相对平坦的带边。这项工作为探索专门设计的有机阳离子开辟了新途径，以稳定原本无法获得的二维HOIPs，并在光电子学中具有潜在应用。
