Atomic-scale structural mechanisms governing dopant-induced stabilization and photoluminescence enhancement in CsPbI(3) quantum dots.

Revealing the local atomic structure of doped halide perovskite quantum dots (QDs) is crucial for understanding how metal-ion incorporation tunes their optoelectronic properties. In particular, dopant-lattice interactions in CsPbI are governed by short-range distortions and dynamic lattice fluctuations that cannot be resolved by conventional diffraction methods. Here, we present a systematic investigation of Zn-doped CsPbI QDs over a wide Zn : Pb ratio (0-1.5) by combining optical spectroscopy with extended X-ray absorption fine structure (EXAFS) and X-ray total scattering analyses. An optimal Pb : Zn ratio of 1 : 1.25 yields a markedly enhanced photoluminescence quantum yield of up to 97%, accompanied by shortened carrier lifetimes, whereas excessive Zn doping deteriorates the optical performance. EXAFS reveals shortened Pb-I bond lengths, a general increase in coordination numbers, and reduced local octahedral distortion in Zn-doped samples compared with pristine CsPbI QDs. Complementary pair distribution function (PDF) analysis demonstrates PbI octahedral tilting and decreased atomic displacement parameters, indicating stabilisation of lattice fluctuations. These structural modifications collectively weaken electron-phonon coupling and suppress non-radiative recombination pathways, thereby accounting for the enhanced emission efficiency. This work establishes a direct correlation between dopant-induced local structural stabilisation and optoelectronic performance in CsPbI QDs.