Reduction of Hole Carriers by van der Waals Contact for Enhanced Photoluminescence Quantum Yield in Two-Dimensional Tin Halide Perovskite

The role of electronicdoping in determining the luminescence efficiencyof low-dimensional halide perovskites has been challenging to testdue to the structural complexity resulting from conventional dopantuse. In this study, we demonstrate that van der Waals contact of aluminum(Al) onto a two-dimensional tin halide perovskite, phenethylammoniumtin iodide (PEA(2)SnI(4)), enhances photoluminescence(PL) intensity significantly, reaching a record-high PL quantum yieldof 10%. The intensity relies on the contact metal type and revertswhen the contact is released, demonstrating structural invariability.Ultraviolet photoemission spectroscopy reveals a 0.6 eV Fermi-levelupshift caused by the Al contact, indicating a reduced hole concentration.Incident power-dependence and time-resolved PL suggest trap-assistedrecombination as the primary nonradiative pathway. The Shockley-Read-Halltheory predicts suppression of trap-assisted recombination due toreduced free carrier concentration, providing a quantitative explanationfor our findings. Our study emphasizes the significance of controllingelectronic doping to optimize luminescence efficiency in low-dimensionalperovskites.