Hoffman Justin M, Che Xiaoyang, Sidhik Siraj, Li Xiaotong, Hadar Ido, Blancon Jean-Christophe, Yamaguchi Hisato, Kepenekian Mikaël, Katan Claudine, Even Jacky, Stoumpos Constantinos C, Mohite Aditya D, Kanatzidis Mercouri G
Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States.
Univ Rennes, ENSCR, INSA Rennes, CNRS , ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226 , Rennes F-35000 , France.
J Am Chem Soc. 2019 Jul 10;141(27):10661-10676. doi: 10.1021/jacs.9b02846. Epub 2019 Jun 27.
Two-dimensional (2D) hybrid halide perovskites are promising in optoelectronic applications, particularly solar cells and light-emitting devices (LEDs), and for their increased stability as compared to 3D perovskites. Here, we report a new series of structures using propylammonium (PA), which results in a series of Ruddlesden-Popper (RP) structures with the formula (PA)(MA)PbI ( = 3, 4) and a new homologous series of "step-like" (SL) structures where the PbI octahedra connect in a corner- and face-sharing motif with the general formula (PA)(MA)PbI ( = 2, 3, 4). The RP structures show a blue-shift in bandgap for decreasing (1.90 eV for = 4 and 2.03 eV for = 3), while the SL structures have an even greater blue-shift (2.53 eV for = 4, 2.74 eV for = 3, and 2.93 eV for = 2). DFT calculations show that, while the RP structures are electronically 2D quantum wells, the SL structures are electronically 1D quantum wires with chains of corner-sharing octahedra "insulated" by blocks of face-sharing octahedra. Dark measurements for RP crystals show high resistivity perpendicular to the layers (10 Ω cm) but a lower resistivity parallel to them (10 Ω cm). The SL crystals have varying resistivity in all three directions, confirming both RP and SL crystals' utility as anisotropic electronic materials. The RP structures show strong photoresponse, whereas the SL materials exhibit resistivity trends that are dominated by ionic transport and no photoresponse. Solar cells were made with = 3 giving an efficiency of 7.04% (average 6.28 ± 0.65%) with negligible hysteresis.
二维（2D）混合卤化物钙钛矿在光电子应用领域，特别是太阳能电池和发光器件（LED）中具有广阔前景，并且相较于三维钙钛矿，其稳定性有所提高。在此，我们报道了一系列使用丙基铵（PA）的新结构，这产生了一系列通式为(PA)(MA)PbI（n = 3, 4）的Ruddlesden-Popper（RP）结构，以及一个新的同系“阶梯状”（SL）结构系列，其中PbI八面体以角共享和面共享的方式连接，通式为(PA)(MA)PbI（n = 2, 3, 4）。对于减小的n值，RP结构的带隙呈现蓝移（n = 4时为1.90 eV，n = 3时为2.03 eV），而SL结构的蓝移更大（n = 4时为2.53 eV，n = 3时为2.74 eV，n = 2时为2.93 eV）。密度泛函理论（DFT）计算表明，虽然RP结构在电子上是二维量子阱，但SL结构在电子上是一维量子线，角共享八面体链被面共享八面体块“绝缘”。对RP晶体的暗态测量表明，垂直于层的电阻率较高（10⁶ Ω·cm），但平行于层的电阻率较低（10³ Ω·cm）。SL晶体在所有三个方向上的电阻率各不相同，证实了RP和SL晶体作为各向异性电子材料的实用性。RP结构表现出强烈的光响应，而SL材料的电阻率趋势主要由离子传输主导，且无光响应。以n = 3制备的太阳能电池效率为7.04%（平均6.28 ± 0.65%），滞后可忽略不计。
