Effect of Mn²⁺ Doping on the Photoluminescence of Hybrid One-Dimensional Lead Halide Post-Perovskites

Although organic-inorganic hybrid one-dimensional (1D) lead halide postperovskites (LHPPs) have been reported to show white luminescence and tunable photoluminescence quantum yield (PLQY), their structure-property relationships are not fully understood. Here, we used Mn²⁺ to test the doping effect on the luminescence of two 1D-LHPPs compounds, namely, {TETA[Pb₂Br₆]}_n 1 and {TETA[Pb₂Cl₆]}_n 2, where TETA = triethylenetetrammonium. We found the pristine compounds show yellowish (551 nm) and bluish (447 nm) emission for 1 and 2, respectively, nanosecond excitation lifetimes (4.17 ns for 1 and 2.29 ns for 2) and low PLQYs (4.65 and 3.57% for 1 and 2, respectively). By fine-doping the Mn²⁺ ions to ca. 8% the PLQYs for 1 and 2 are maximized to 24 and 25% for 1 and 2, respectively. Upon the increasing Mn²⁺ dopant, the emission wavelengths can also vary gradually from 551 to 615 nm and from 447 to 660 nm for 1 and 2, respectively, covering almost the whole visible-light range, and the excitation lifetimes are enhanced to microseconds (0.77 μs for 1 and 0.39 μs for 2), owing to the more spin-forbidden d-d transition (⁴T₁-⁶A₁) component from the Mn²⁺ ions present in the photoluminescence spectra. Moreover, these Mn²⁺-doped 1D-LHPPs demonstrate high structural and optical stability in humid and high-temperature environments. Hence, such doped materials can be fabricated into a UV-pumped white light-emitting diode, rendering the potential application for solid-state lighting and display systems.