Compared with their three-dimensional (3D) counterparts, low-dimensional metal halide perovskites (2D and quasi-2D; B2An−1MnX3n+1, such as B = R-NH3+, A = HC(NH2)2+, Cs+; M = Pb2+, Sn2+; X = Cl−, Br−, I−) with periodic inorganic–organic structures have shown promising stability and hysteresis-free electrical performance1–6. However, their unique multiple-quantum-well structure limits the device efficiencies because of the grain boundaries and randomly oriented quantum wells in polycrystals7. In single crystals, the carrier transport through the thickness direction is hindered by the layered insulating organic spacers8. Furthermore, the strong quantum confinement from the organic spacers limits the generation and transport of free carriers9,10. Also, lead-free metal halide perovskites have been developed but their device performance is limited by their low crystallinity and structural instability11. Here we report a low-dimensional metal halide perovskite BA2MAn−1SnnI3n+1 (BA, butylammonium; MA, methylammonium; n = 1, 3, 5) superlattice by chemical epitaxy. The inorganic slabs are aligned vertical to the substrate and interconnected in a criss-cross 2D network parallel to the substrate, leading to efficient carrier transport in three dimensions. A lattice-mismatched substrate compresses the organic spacers, which weakens the quantum confinement. The performance of a superlattice solar cell has been certified under the quasi-steady state, showing a stable 12.36% photoelectric conversion efficiency. Moreover, an intraband exciton relaxation process may have yielded an unusually high open-circuit voltage (VOC).
|Number of pages||7|
|Publication status||Published - 2022 Aug 11|
Bibliographical noteFunding Information:
We thank S. Xiang for constructive feedback on preparing the manuscript and D. Fenning for inspiring discussions on the data analysis. This work was supported by a Sloan Research Fellowship from the Alfred P. Sloan Foundation and a Lattimer Faculty Research Fellowship from the University of California, San Diego. The microfabrication involved in this work was performed at the San Diego Nanotechnology Infrastructure (SDNI) of the University of California, San Diego, a member of the National Nanotechnology Coordinated Infrastructure, which was supported by the National Science Foundation (grant no. ECCS-1542148). This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the US Department of Energy, Office of Science at Los Alamos National Laboratory, Stanford Nano Shared Facilities (SNSF, supported by the National Science Foundation under award ECCS-1542152) and Stanford Synchrotron Radiation Laboratory (SSRL, a national user facility operated by Stanford University on behalf of the US Department of Energy, Office of Basic Energy Sciences). The computational work used the Extreme Science and Engineering Discovery Environment (XSEDE), which was supported by the National Science Foundation (grant number OCI-1053575). F.B. acknowledges support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under award number DE-SC0021266. Y.W. acknowledges support from the Office of Naval Research (award N00014-19-1-2453) and the Molecular Foundry, which was supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under contract no. DE-AC02-05CH11231.
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