Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
DOI: https://doi.org/10.29363/nanoge.hopv.2022.087
Publication date: 20th April 2022
Two-dimensional (2D) hybrid double perovskites are a promising emerging class of materials featuring superior intrinsic and extrinsic stability over their three-dimensional (3D) parent structures, while enabling additional structural diversity and tunability.[1] Here, we expand the Ag-Bi based double perovskite system, comparing structures obtained with the halides chloride, bromide and iodide and the organic spacer cation 4-fluorophenethylammonium (4FPEA) to form the n = 1 Ruddlesden-Popper (RP) phases (4FPEA)4AgBiX8 (X = Cl, Br, I). We demonstrate access to the iodide RP-phase through a simple organic spacer, analyze the different properties as a result of halide substitution and incorporate the materials into photodetectors. Highly oriented thin films with very large domain sizes are fabricated and investigated with grazing incidence wide angle X-ray scattering, revealing a strong dependence of morphology on substrate choice and synthesis parameters. First-principles calculations confirm a direct band gap and show type Ib and IIb band alignment between organic and inorganic quantum wells. Optical characterization, temperature-dependent photoluminescence and optical-pump terahertz-probe spectroscopy give insights into the absorption and emissive behavior of the materials as well as their charge-carrier dynamics. Overall, we further elucidate the possible reasons for the electronic and emissive properties of these intriguing materials, dominated by phonon-coupled and defect-mediated polaronic states.