Li Hong,Zaiwei Wang,Jovana V. Milić,Claudia E. Avalos,Weihua Zhang,Dan Ren,Cheng Wang,Brian Carlsen,Yuhang Liu,Shaik Mohammed Zakeeruddin,Anders Hagfeldt,Ti Wang,Hongwei Han,Michael Graetzel
Two-dimensional (2D) hybrid perovskite solar cells have induced widespread research interest owing to their higher stability as compared to three-dimensional (3D) analogues. The photovoltaic performance, however, is still limited. Here, we report a perovskite film dominated by 3D components that are modulated by formamidinium thiocyanate in the 2D PEA2FA3Pb4I13 perovskite composition. We demonstrate that a dimensionality transformation from a 2D/3D to predominantly 3D perovskite phase in the presence of SCN-based treatment enhances the optical absorption in visible and near-infrared regions. As a result, the power conversion efficiency improved 4.5 times with respect to the control to above 14%. The unencapsulated cell exhibited excellent moisture stability during the shelf lifetime measurement over 70 days under ambient conditions.
The structural information of a material in both the solid state and solution state is essential to the in-depth understanding of the properties of inorganic–organic hybrid materials. A one-dimensional (1D) lead bromide formulated as [H][NH3(CH2)2SS(CH2)2NH3][H2O][PbBr5] (1) could be converted into a new two-dimensional (2D) complex, [NH3(CH2)2SS(CH2)2NH3][PbBr4] (2), by soaking the crystals in water. The isolated 2D compound showed single-layer lead-halide perovskite structures. Electrospray ionization mass spectrometry (ESI-MS) analyses of the reaction solution revealed that the [PbBr3]− fragments are initially formed from the rapid decomposition of the 1D [PbBr5]3− chains and subsequently reassemble into 2D [PbBr4]2− layers, which was verified by powder X-ray diffraction (PXRD) and microcalorimetry. Because of the decomposition and reassembly process, complex 1 could be used as a precursor to synthesize M2+-doped 2D lead bromide perovskites, namely, Mn@2, Ni@2 and Cd@2. In addition, preliminary tests indicated that complex 2 exhibited a lower optical band gap (3.25 eV) and higher electrical conductivity (3.2 × 10−11 S cm−1) than complex 1 (3.38 eV, 5.4 × 10−12 S cm−1).
Lead free double perovskites (DPs) are promising materials due to their non-toxic and tunable optical properties. In this work, a series of lead-free halide DP single crystals (SCs) and nanocrystals (NCs) (Cs4Cu1-xAg2xSb2Cl12) were reported. With alloying strategy, the optical band-gap engineering was realized and the dimension can be controlled between 2D and 3D. The Cu-alloyed SCs exhibit strong absorption from the UV-visible region to the near-infrared range (can even completely cover the bands of NIR-I and NIR-II). In addition, (Cs4Cu1-xAg2xSb2Cl12) NCs were synthesized via a top-down approach, which maintains similar optical properties and the dimensional transformation phenomenon to SCs. These results suggest the great potential of Cs4Cu1-xAg2xSb2Cl12 SCs and NCs for photovoltaic and optoelectronic applications.
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