The materials that have enabled the information technology revolution over the past decades will soon reach their physical limits. Novel nanomaterials and technologies have therefore become a major focus of current solid-state device research, with two-dimensional (2D) atomic crystals being one of the most promising candidates. Graphene, a 2D structure of carbon atoms with unorthodox electronic properties, is the most prominent representative of the 2D material family. More recently, transition metal dichalcogenides (TMDs) have come into the focus of interest, as these offer properties that complement those of graphene. Some TMDs are semiconductors with a sizable bandgap, which allows the construction of logic transistors, light emitters, photovoltaic solar cells, and other devices. In the first part of this talk, I will preset some of our spectroscopic studies on linear and nonlinear optical properties of 2D semiconductors, including polarization-resolved second harmonic measurements that show strain-induced modifications of the second harmonic pattern, and single photon emission from localized exciton states. I will then review our activities on photovoltaic energy conversion, photon detection and electrically driven light emission in TMDs. Finally, the development of electronic circuits based on 2D materials will be discussed. Large-area MoS₂ monolayer-film growth by chemical vapor deposition, together with the development of 2D logic stages, enabled us to realize the first large-scale digital integrated circuit based on a 2D material. It is envisioned that the excellent material quality, combined with the advantages of 2D materials, such as flexibility, high mechanical stability and low costs of production, could lead to new electronic and optoelectronic technologies.