Enhanced Low-Temperature Photoluminescence in α-CsPbI₃/WS₂ Heterostructures: Experimental and Theoretical Insights...

Two-dimensional transition metal dichalcogenides (TMDCs) show great promise for photonic and optoelectronic technologies. However, non-radiative recombination channels in TMDCs limit their photoluminescence (PL) quantum yield. Despite various enhancement strategies, the fundamental mechanisms governing TMDC emission enhancement remain unclear. Here, we demonstrate that heterostructure engineering by spin-coating cesium lead iodide (α-CsPbI₃) perovskite quantum dots, with high optical absorption, onto tungsten disulfide (WS₂) monolayer, leads to 109-fold enhanced PL intensity at 8 K compared to 300 K. Using PL spectroscopy, we investigated the temperature-dependent tunability of the PL intensity and unraveled how structural distortions in α-CsPbI₃ dynamically modulate charge transfer processes and radiative recombination. Density functional theory (DFT) and non-equilibrium Green's function (NEGF)-DFT calculations confirm that at 8 K, structural distortions in α-CsPbI₃ and phonon interactions are both reduced, lowering electron and hole transport barriers, enhancing carrier transmission to WS₂, and thereby promoting biexciton formation and ultrahigh PL. Conversely, at 300 K, increased structural distortions elevate the barrier, favor trion formation, and quench the PL. These findings establish temperature-driven structural shifts as a novel mechanism for engineering hybrid QD/TMDC materials with tunable optical properties. Our combined experiments and theoretical calculations provide foundational insights for next-generation low-temperature quantum devices and hybrid QD/TMDC systems.