Two-dimensional (2D) van der Waals materials including graphene, hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDCs) such as MoS₂ and WSe₂ have great potential for exploring the exotic quantum behaviors and realization of advanced optoelectronics devices. Especially, ultrafast light emitter in nanoscale is a critical component in the development of the high bandwidth on-chip optical interconnects. However, previous technology faces the major challenges such as big footprint, high cost integration and difficulties of direct high speed electrical pumping. Here, I will talk the first electrically driven ultrafast graphene light emitter that exhibits the ultrafast light modulation up to ~ 10 GHz with broad spectral range (visible to near infrared). Atomically thin hBN encapsulation layers to graphene allow the stable and practical high performance even under the ambient condition as well as efficient direct electronic cooling via near-field coupling of hybrid plasmon-phonon polaritonic modes. Ultrafast and broadband graphene light emitter paves the way towards the realization of complete graphene-based ultrafast optical communications. I will also present the near UV (~390nm) electroluminescence (EL) and broadband photodetection from hBN heterostructures. Near UV EL in hBN are attributed to the electric field induced artificial color centers, which are vacancy-related defects with an excitonic mode in the intrinsic band gap of hBN (> 6 eV). These results demonstrate the promise of hBN-based van der Waals heterostructures for light sources and optoelectronics in the near UV to the visible regime.