Mn-Doped CsPbCl₃ Perovskite Nanocrystal via Surface Engineering with Thiophene-2-Carboxylic Acid: Implications for Photoresponse Study

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The Mn-doped CsPbCl3 achieved more attention to improving the photophysical properties of CsPbCl3 and dual emission. Mn-doping in CsPbCl3 cannot match its PLQY with other inorganic lead halide perovskites. The PLQY of Mn-doped CsPbCl3 improved by codoping other metal ions and mixing with other halides, but the postsynthesis surface passivation approach needs to be better explored. The current study explores the potential of TCA as a surface engineering agent for Mn-doped CsPbCl3 perovskite films. The lone pair electrons of the sulfur atom in TCA interact with the under-coordinated Pb ions on the perovskite surface and passivate the surface defects in perovskites. The XRD pattern and TEM images confirmed that TCA passivation did not affect the crystallinity and particle size. The interaction of TCA is confirmed by XPS analysis. The introduction of TCA suppressed nonradiative recombination and enhanced the photophysical properties. Photoluminescence spectra and lifetime decay profiles confirm the passivation effect of TCA. The relative PLQY of Mn-doped CsPbCl3 increased from 21% to 50%, and the lifetime increased from 8.70 to 9.56 ns. The TCA passivated Mn-CsPbCl3 showed better photoresponsivity than the unpassivated one as the surface defect states were reduced.