Highly Bright Silicon Nanocrystal White Light-Emitting Diodes With Luminance in Excess of 10000 cd m⁻2

Abstract

Silicon (Si) light source has profound significance in monolithic integrated Si photonics. However, its luminance remains too low to meet practical use that usually requires > 10000 cd m⁻². Here, an all-inorganic Si nanocrystal (SiNC) white light-emitting diode (WLED) with a continuous emission spectrum spanning ≈400–900 nm in wavelength, is reported. The architecture of the WLED comprises front electrode of Ag grids and transparent-conducting-oxide/electron transport layer (ETL) of ZnO/front charge confinement layer (CCL) of SiO₂/active layer of low-resistivity SiNC composite thin film/rear CCL of SiO₂/hole transport layer (HTL) of MoO₃/textured p-Si substrate/rear electrode of aluminum/heat radiator. The main procedures for achieving high luminance here include combined applications of high-pressure ammonia passivation of the active layer, which enhances its photoluminescence quantum yield significantly, and texturing of p-Si substrate, which boosts the light extraction and charge injection effectively. With an optimized combination of passivation and texturing, luminance of 10751 cd m⁻² is achieved with external quantum efficiency (EQE) of 0.26%. After a Peltier cooler is further applied, luminance of 12363 cd m⁻² is attained with EQE of 0.30%. Following further technical iterations, this highly bright SiNC WLED shall find applications in monolithic integrated Si photonics and even Si general lighting.