M-C Tang, S. Zhang, C.A. Hacker
National Institute of Standards and Technology (NIST),
Keywords: 2D Perovskites, Solar Cells, X-ray photoemission spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS)
Summary:Organic-inorganic two-dimensional (2D) layered hybrid perovskites have attracted immense attention because of their remarkable optoelectronic properties, including high absorption coefficient, long exciton diffusion length, and tunable direct bandgap. Beyond traditional low bandgap 3D hybrid perovskite solar cells, namely methylammonium lead triiodide (MAPbI3), 2D layered hybrid perovskites have demonstrated a wide and tunable bandgap, suitable not only for semitransparent and transparent solar cells applications but also for blue and ultraviolet light-emitting diode and photodetector applications. In this contribution, we systematically investigate electronic structure, composition, and optoelectronic properties of 3 different materials systems including 3D, 2D layered and 2D/3D heterojunction structure perovskites (as shown in Figure 1). Our previous work on 3D systems showed a clear link between morphology, composition, electronic structure, and device properties. We extend our knowledge of 3D processing to investigate confined 2D systems and the 2D/3D hybrid systems. We employ a multi-probe investigation method consisting of X-ray photoemission spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) complemented with morphology and X-ray powder diffraction (XRD) characterization of 2D layered and 2D/3D hierarchical structure perovskites to understand the trend of solar cell performance. Obtained results reveal the composition distribution, polycrystalline structure and morphology of 2D layered and 2D/3D hierarchical structure perovskite thin films. We use this insight to develop a composition engineering protocol suitable for depositing fully covered and pin-hole-free high-quality 2D layered and 2D/3D hierarchical structure perovskite thin films and present efficient single-junction photovoltaics with high stability for future industrial scale‐up fabrication.