Browsing by Author "Mladenović, Marko"

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    Atomic-Level Microstructure of Efficient Formamidinium-Based Perovskite Solar Cells Stabilized by 5-Ammonium Valeric Acid Iodide Revealed by Multinuclear and Two-Dimensional Solid-State NMR
    Alanazi, Anwar Q.; Kubicki, Dominik J.; Prochowicz, Daniel; Alharbi, Essa A.; Bouduban, Marine E. F.; Jahanbakhshi, Farzaneh; Mladenović, Marko; Milić, Jovana; Giordano, Fabrizio; Ren, Dan; Alyamani, Ahmed Y.; Albrithen, Hamad; Albadri, Abdulrahman; Alotaibi, Mohammad Hayal; Moser, Jacques-E.; Zakeeruddin, Shaik M.; Rothlisberger, Ursula; Emsley, Lyndon; Grätzel, Michael
    Chemical doping of inorganic-organic hybrid perovskites is an effective way of improving the performance and operational stability of perovskite solar cells (PSCs). Here we use 5-ammonium valeric acid iodide (AVAI) to chemically stabilize the structure of α-FAPbI3. Using solid-state MAS NMR, we demonstrate the atomic-level interaction between the molecular modulator and the perovskite lattice and propose a structural model of the stabilized three-dimensional structure, further aided by density functional theory (DFT) calculations. We find that one-step deposition of the perovskite in the presence of AVAI produces highly crystalline films with large, micrometer-sized grains and enhanced charge-carrier lifetimes, as probed by transient absorption spectroscopy. As a result, we achieve greatly enhanced solar cell performance for the optimized AVA-based devices with a maximum power conversion efficiency (PCE) of 18.94%. The devices retain 90% of the initial efficiency after 300 h under continuous white light illumination and maximum-power point-tracking measurement.
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    Effects of thermal disorder on the electronic structure of halide perovskites: Insights from MD simulations
    Mladenović, Marko; Vukmirović, Nenad
    The effects of thermal disorder on the electronic properties of organic/inorganic halide perovskites were investigated using ab initio molecular dynamics simulations. It was generally found that band gap variations due to effects of thermal disorder are the largest in materials with the smallest lattice constant. The factors that may lead to departure from this trend include the degree of rotational and translational motion of the organic cation and the strength of its dipole. It was found that the contribution of the flexible organic part to the band gap variations is considerably smaller than the contribution of the inorganic part of the material. The results of our simulations indicate that band gap variations in halide perovskites fall within the range exhibited in inorganic semiconductors.