Pressure-Engineered Optical and Charge Transport Properties of Mn/Cu Codoped CsPbCl Perovskite Nanocrystals Structural Progression.

In this work, compared with the corresponding pure CsPbCl nanocrystals (NCs) and Mn-doped CsPbCl NCs, Mn/Cu-codoped CsPbCl NCs exhibited improved photoluminescence (PL) and photoluminescence quantum yields (PL QYs) (57.6%), prolonged PL lifetimes (1.78 ms), and enhanced thermal endurance (523 K) as a result of efficient Mn doping (3.66%) induced by the addition of CuCl. Furthermore, we applied pressure on Mn/Cu-codoped CsPbCl NCs to reveal that a red shift of photoluminescence followed by a blue shift was caused by band gap evolution and related to the structural phase transition from cubic to orthorhombic. Moreover, we also found that under the preheating condition of 523 K, such phase transition exhibited obvious morphological invariance, accompanied by significantly enhanced conductivity. The pressure applied to the products treated with high temperature enlarged the electrical difference and easily intensified the interface by closer packaging. Interestingly, defect-triggered mixed ionic and electronic conducting (MIEC) was observed in annealed NCs when the applied pressure was 2.9 GPa. The pressure-dependent ionic conduction was closely related to local nanocrystal amorphization and increased deviatoric stress, as clearly described by impedance spectra. Finally, retrieved products exhibited better conductivity (improved by 5-6 times) and enhanced photoelectric response than those when pressure was not applied. Our findings not only reveal the pressure-tuned optical and electrical properties structural progression but also open up the promising exploration of more amorphous all-inorganic CsPbX-based photoelectric applications.