Search for: All records

Silicon’s indirect band gap severely suppresses radiative recombination, limiting its use as an efficient light-emitting material. Although nanoscale confinement of carriers, dielectric resonators, or plasmonic structures can partially mitigate this limitation, these approaches typically require complex fabrication. Here, we report a fundamentally different and scalable mechanism that enables efficient light emission directly from bulk silicon. By decorating a silicon wafer with ultrasmall (<2 nm) gold or copper particles, we observe intense luminescence spanning the visible and near-infrared. Remarkably, the emission is indistinguishable for Au and Cu decorations in both spectral and temporal domains, demonstrating that the confinement extent, not the material composition, governs the effect. We attribute the emission to spatially confined photonic states with broadened momentum distributions, enabling phonon-independent optical transitions otherwise forbidden in silicon. This mechanism yields quantum efficiencies comparable to those of direct-band-gap semiconductors and produces ∼a 10^5-fold enhancement in the integrated emission intensity, establishing a practical route toward silicon light-emitting devices. 

Molecular materials offer a boundless design palette for light absorption and charge transport in both natural photosynthesis and engineered photovoltaics. They function in combination as chromophores, donors, conductors, and acceptors, enabling the excitation and charge carrier transport through space and wire-like intramolecular pathways. Although quantum coher- ence is believed to enhance photoexcitation and photoinduced charge transfer, fluctuating and inhomogeneous environments accelerate decoherence. Here, we assemble a nanoporous medium consisting of a templated bipyridyl ethylene (BPE) molecule array on a Ag(111) surface that functions as an exceptional intermolecular nonnuclear quantum well conductor of coherent electron waves spanning over 20 Å length. Time-periodic driving of the Ag/BPE interface by femtosecond pulses promotes electrons into a ladder of Floquet quasi-energy donor states, where intermolecular quantum well states act as a resonant doorway for coherent electron transport into BPE/vacuum image potential acceptor states. The bifurcation of electron passage between the Floquet donor ladder and the charge transfer acceptor channel is recorded by projecting the active electrons into the photoemission continuum in an interferometric time- and angle-resolved multiphoton photoemission experiment. We find that exceptional decoupling of electrons from the metal substrate by the molecule- dressed vacuum preserves the coherence on the ∼150 fs time scale. This offers a new paradigm for quantum state design where a molecule-dressed vacuum mediates coherent electron transport in nanoporous molecular architectures.