Pressure tailoring electron-phonon coupling toward enhanced yellow photoluminescence quantum yield and piezochromism

Improvements in yellow light production, a healthy light source for the eyes that is also beneficial to biological growth, are needed to satisfy the practical requirements of solid-state lighting. Here, we report high-brightness yellow light emission in zero-dimensional lead-free double-perovskite Rb2TeCl6 microcrystals (MCs) driven by high-pressure processing. We note that the photoluminescence quantum yields (PLQYs) experience a significant enhancement by an order of magnitude upon a mild pressure of 1.7 GPa. The overlap between ground state and self-trapped state is reduced by pressure-tailored electron-phonon coupling. Accordingly, the phonon-assisted non-radiative relaxation is inhibited, resulting in a considerable increase in PLQY. Furthermore, marked piezochromism from pale yellow to green is realized in compressed Rb2TeCl6 MCs. Our study not only enables pressure as a robust tool to boost yellow light efficiency but also provides deep insights into the underlying photophysical mechanism, facilitating the rational synthesis of materials by design.