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Single-particle optical study on the effect of chloride post-treatment of MAPbI(3) nano/microcrystals

  • Jin, Handong;
  • Mukherjee, Amitrajit;
  • Chouhan, Lata; 148703;
  • Steele, Julian A; 109116;
  • de Jong, Flip; 125355;
  • Gao, Yujie;
  • Roeffaers, Maarten BJ; 46986;
  • Hofkens, Johan; 11681;
  • Debroye, Elke; 69619;
Publication Date
Mar 16, 2023
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Surface passivation by post-treatment with methylammonium chloride (MACl) is regarded as a promising strategy to suppress surface defects in organic-inorganic lead halide perovskites and elevate the efficiency of solar cells based on these materials. However, traditional MACl post-treatment methods often impede the performance of the final device, due to the creation of additional unwanted defects. Herein, we report a novel approach for chloride post-treatment by applying a mixed ethanol/toluene solvent and validate its beneficial effect on the structure, composition, and optical properties of methylammonium lead iodide nano/microcrystals and related photosensitive devices. An optimized (mild) Cl content improves the crystallinity, enhances photoluminescence (PL) intensity, provides longer PL lifetimes, and induces brighter and longer ON-states in single-particle emission trajectories. On top of a reduction in the population percentage of crystals showing gradual photodegradation, our Cl-treatment method even leads to photobrightening. Additionally, the extent of carrier communication throughout spatially distant nanodomains enhances after MACl-based post-modification. Our results demonstrate that surface-bound Cl significantly reduces the trap density induced by under-coordinated lead ions or iodide vacancies and reveal the importance of a careful consideration of the applied Cl content to avoid the generation of high-bandgap MAPbCl3 heterojunctions upon excessive Cl treatment. Importantly, significant trap passivation upon MACl treatment translates into a more stable and elevated photocurrent in the corresponding photodetector device. We anticipate these findings will be beneficial for designing durable, high-performance lead halide perovskite photonic devices. / status: published

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