Engineering two-dimensional (2D) / three-dimensional (3D) perovskites has emerged as an attractive route to efficient and durable perovskite solar cells. Beyond improving the surface stability of the 3D layer and acting as a trap passivation agent, the exact function of 2D/3D device interface remains vague. Here, we provide evidence that 2D/3D perovskite interface that forms a p-n junction is capable to reduce the electron density at the hole-transporting layer interface and ultimately suppress interfacial recombination. By a novel ultraviolet photoelectron spectroscopy (UPS) depth-profiling technique, we show that engineering of the 2D organic cations, in this case by simply varying the halide counter ions in thiophene methylammonium-salts, modifies the 2D/3D perovskite energy alignment. These measurements enable the true identification of the energetic across the 2D/3D interface, so far unclear. When integrated in solar cells, due to the electron blocking nature of the 2D layer, the optimized 2D/3D structures suppress the interfacial recombination losses, leading to open-circuit voltage (VOC) which approaches the potential internal Quasi-Fermi Level Splitting (QFLS) voltage of the perovskite absorber. The devices exhibit an improved fill factor (FF) driven by the enhanced hole extraction efficiency and reduced electron density at the 2D/3D interface. We thus identify the essential parameters and energetic alignment scenario required for 2D/3D perovskite systems in order to surpass the current limitations of hybrid perovskite solar cell performances.
Article
2D/3D Perovskite Engineering Eliminates Interfacial Recombination Losses in Hybrid Perovskite Solar Cells
https://doi.org/10.21203/rs.3.rs-51900/v1
This work is licensed under a CC BY 4.0 License
Journal Publication
published 01 Jul, 2021
Version 1
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2D/3D Perovskite Engineering Eliminates Interfacial Recombination Losses in Hybrid Perovskite Solar Cells
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XRD patterns of 3D perovskite films as the control.
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UV-Vis absorption spectra of 2D/3D perovskite thin films based on 2-TMAI, 2-TMABr, and 2-TMACl, and 3D control.
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Photoluminescence spectra of the 3D control film (a), 2D/3D films employing 2-TMAI (b), 2-TMABr (c), and 2-TMACl (d) upon top (2D perovskite side) and bottom side (3D perovskite side) excitation exciting at 450 nm.
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Comparison of the Voc measurement with and without metal mask of the 3D control PSC and 2D/3D PSCs employing 2-TMAI, 2-TMABr, and 2-TMACl cations.
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Drift-diffusion simulation for different system investigate in this work. a-c Simulated band structure of the 3D perovskite device as the control (a), the 2D/3D system implementing 2-TMABr as cation (b), and the 2D/3D system implementing 2- TMACl (c). Notably, in the image, the thickness of the transport layer is artificially reduced compared to the true simulation values, in order to better visualize the perovskite interfaces. d-f Electron and hole density in the different layers of the device for the corresponding three systems in a-c. g,h Drift diffusion simulation J-V for the system depicted in a-c.
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a. PL spectra of neat perovskite materials. b. PL spectra of perovskite solar cells devices. c PLQY of neat perovskite materials and solar cells devices.
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Hysteresis measurement between reverse scan (RS) and forward scan (FS) of the 3D control device (a), 2D/3D PSCs employing 2-TMAI (b), 2-TMABr (c), and 2-TMAI (d).
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External quantum efficiency (EQE) of 2D/3D PSCs based on 2- TMAI, 2-TMABr, and 2-TMACl, and 3D control.
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UPS spectrum of the 3D perovskite as the control.
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Statistics of the photovoltaics parameters of 3D control and 2D/3D PSCs based on 2-TMAI, 2-TMABr, and 2-TMACl over 74 devices.
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Photovoltaics parameters of 3D control and 2D/3D PSCs based on 2-TMAI, 2-TMABr, and 2-TMACl upon the hysteresis scan.
