Hybrid organic–inorganic perovskites (HOIPs) have gained substantial attention due to their excellent photovoltaic and optoelectronic properties.

Ethylammonium lead iodide (C2H5NH3PbI3) with a unique one-dimensional structure is presented as a new organic–inorganic halide perovskite among the emerging photoactive materials. Here, we have discovered that C2H5NH3PbI3 can easily undergo structural distortion and enable a strong quantum confinement that generates double emission enhancement and gives a 5-fold enhanced broadband emission under pressure. Experimental data analyses indicate that the decrease in the conduction band energy caused by the shortening of the Pb–I bond length contributes to the first increase of the emission at 2.7 GPa. The second enhancement of the emission is triggered at 4.5 GPa, induced by the increased self-trapping depth rooting in the strong coupling between the distorted PbI6 octahedral inorganic lattice and excitons after the phase transition from orthogonal to monoclinic structure. This work verifies that pressure is a powerful way to create one-dimensional systems favorable for exciton self-trapping for producing enhanced broadband emission, and opens up a new route toward superior light emitters based on quantum materials.

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Yellow fluorescent materials (emitting at wavelengths 580–595 nm) offer outstanding functionality for vivid displays, high-density information storage, and high-pressure lighting, especially in white-light-emitting diodes. Currently, the deliberate design of yellow phosphors with high photoluminescence quantum yields (PLQYs) is a developing field. Herein, we report high yellow emission in two-dimensional (2D) halide PA8Pb5I18 (PA = C3H7NH3) perovskite that shows over 80-fold enhancement of their PL under pressure. At an applied pressure of 3.5 GPa, PA8Pb5I18 produces a high PLQY of 77.0% and a color coordinate (0.55, 0.44) closely approaching the standard sodium yellow light (0.575, 0.424). Structural and optical measurements reveal that pressure-induced tilt of the octahedra along the I 4–I 2 axis is attributable to the deepening of trap states in the quantum well structures, leading to a significant Stokes shift. The resulting more localized excitons have a lower probability of scattering with defects, which results in significant suppression of nonradiative loss and promotion of radiative recombination rate, accounting for the efficient and high-color-purity emission. Our findings represent a deep insight into the photophysical nature of 2D halide perovskites, thus offering a promising strategy for the rational design of high-efficiency yellow phosphors.