Broadband Photo- and Electroluminescence from Bulk Silicon via Strong Photonic Confinement

Abstract Silicon’s indirect bandgap fundamentally limits its ability to emit light, hindering the development of silicon-based light sources. Here, we demonstrate ultrabroadband photo- and electroluminescence from bulk silicon, enabled by a radiative pathway mediated by momentum-expanded photonic states that bypass phonon-assisted transitions. This mechanism, previously demonstrated using metallic nanoparticles as photon confiners, is here realized in an all-silicon system using embedded sub-1.5 nm silicon crystallites. Combined spectroscopic observations in frequency and time domains, together with all emission trends, are inconsistent with conventional silicon quantum-dot luminescence and instead indicate that ultrasmall crystallites act as photonic confiners enabling radiative recombination in surrounding bulk silicon. The agreement with prior metal-based systems further confirms that confinement size, rather than material composition, governs the activation of radiative transitions in a momentum-forbidden system. The emission spans the visible to near-infrared spectral range, with electroluminescence in an undoped semiconductor device visible under ambient conditions and a quantum efficiency estimated as ∼0.2%. These findings establish a new route to efficient light emission in silicon and reveal a hybrid light-matter regime in which extreme photonic confinement reshapes the electronic transition landscape.