Tunable photoluminescence and an enhanced photoelectric response of Mn-doped CsPbCl perovskite nanocrystals pressure-induced structure evolution

Mn 2+ :CsPbCl 3 nanocrystals (NCs) were synthesized using a modified one-pot injection method, which exhibits significantly improved thermal stability. For the first time, the pressure-treated optical and structural properties of synthetic Mn 2+ :CsPbCl 3 NCs were further investigated, and their associated intriguing electrical and photoelectric properties were revealed from impedance spectra and photocurrent measurements under compression. The pressure-dependent photoluminescence experienced an initial redshift before 1.7 GPa followed by a continuous blueshift, as evidenced by the bandgap shifts. High-pressure XRD spectra uncovered a cubic-to-orthorhombic structural transition at about 1.1 GPa and subsequent amorphization upon further compression, which was fully reversible. Furthermore, the sample annealing from 340 K drove grain growth and decreased grain boundary resistance at ambient pressure. The compression further decreased the grain boundary barrier and improved the electrical conductivity (up to ∼10 −2 Ω −1 cm −1 ) of the thermally annealed Mn 2+ :CsPbCl 3 NC surface. Simultaneous photocurrent enhancement of thermally annealed NCs was also achieved as expected, and reached optimal performance at 0.7 GPa. Strikingly, after the pressure cycling (loading-releasing), the results show that thermally annealed Mn 2+ :CsPbCl 3 NCs gained preservable higher electrical conductivity (∼10 times increase) and an improved photoelectric response compared to the ambient state before compression. This work proves that high pressure is useful for opening the versatility in the structure and properties of metal-halide perovskite nanocrystals leading to a promising way for superior optoelectronic materials-by-design. Pressure-tuned structural, optical and electrical properties are of potential to improve the applied value of Mn 2+ -doped CsPbCl 3 perovskite nanocrystals.