Evaporation-Induced Self-Assembly of Semi-Crystalline PbI 2 (DMSO) Complex Films as a Facile Route to Reproducible and E
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.137
Evaporation-Induced Self-Assembly of SemiCrystalline PbI2(DMSO) Complex Films as a Facile Route to Reproducible and Efficient Planar p-i-n Perovskite Solar Cells Brandon Dunham, Vivek Vattipalli, Christos Dimitrakopoulos
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Department of Chemical Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
ABSTRACT
High quality active layers for hybrid organic-inorganic perovskite solar cells are essential for achieving maximum device performance. However, perovskite active layers in solar cells are frequently prepared with unoptimized processes that lead to layers of inferior quality. This is often the case when research focuses on other aspects of the solar cell device, such as device design and architecture, carrier transport layers, electrodes, interlayers, etc. In this study, a single-step spin-coating method was used to prepare semi-crystalline PbI2(DMSO) complex films via evaporation-induced self-assembly. These optimized intermediate films were then used to form homogeneous methylammonium lead iodide (MAPbI3) perovskite films of optimum thickness (ca. 400 nm) with uniform surface coverage, good crystallinity, high purity, and grain sizes up to one micron, by employing a sequential deposition process involving intramolecular exchange between the PbI2(DMSO) complex film and a methylammonium iodide (MAI) layer deposited on top of it. We found that for certain ranges of MAI concentration, the formation of optimal-quality perovskite active layers was independent of MAI concentration, so long as MAI deposition occurred at specific corresponding spin speeds. Planar p-i-n perovskite solar cells comprising the optimized active layers were fabricated, and they exhibited negligible hysteresis and a maximum power conversion efficiency (PCE) of 16.72%, without any additional compositional and interfacial engineering. The latter can be used in the future to further enhance the PCE. These findings demonstrate the importance of an optimized perovskite active layer for reproducibly fabricating high-efficiency planar p-i-n photovoltaic devices. Additionally, the simplicity of the PbI2(DMSO) complex film preparation and the versatility of the MAI deposition with this fabrication method further enhances the potential of this material for large-scale processing.
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Corresponding author: [email protected]
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INTRODUCTION Depending on the size of the organic cation, organic-inorganic hybrid perovskites can adopt the 3D AMX3 structure, the layered A2MX4 structure, or the mixed layered/3D B2An−1MnX3n+1 [1] structure (where A is a smaller organic cation, M is a divalent metal typically Pb2+ or Sn2+, X is a halide typically Cl-, Br- or I-, B is a larger organic cation, and n is the num
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