The thesis describes the preparation of efficient and simple bright halide perovskite materials and light-emitting devices. In the different chapters, several perovskite types are described and studied: Perovskites with different crystal sizes, from nanosized perovskites (Chapter 2, 3 and 4) to bulk perovskites (Chapter 5) all with a 3D crystal structure; and perovskites with different crystal structure dimensionalities, such as 3D or nanoplatelets with 2D (Chapter 3) and even quasi-2D structures (Chapter 2). Photoluminescence and electroluminescence with colours ranging from red to green and blue are reported. Chapter 2 focuses on obtaining stable and very PL efficient red-emitting hybrid quasi-2D perovskite NCs with a narrow linewidth. The work experiments with a controllable shift of the bandgap, accomplished by varying the chain length of the alkylammonium ligands employed in its synthesis. Chapter 3 describes the novel use of a bifunctional ligand for the synthesis of highly photoluminescent green-emitting MAPbBr3 NPs. Additionally, the ligand allows the nanostructures to effectively anchor on a variety of conducting polymers and inorganic semiconducting surfaces, which is used for the preparation of solution-based multilayer LEDs. Chapter 4 is about green-emitting LEDs with a remarkably high combination of EQE, luminance, power and current efficiency. The outstanding performance is described to be due to an energy cascade from hierarchical self-assembled structures. These structures, low-dimensional octylammonium lead bromide microplatelets (MPLs) and 3D FAPbBr3 NCs, form ultra-smooth films with a very high PLQY. Chapter 5 describes a mechanochemical synthesis of stable mixed-cation/mixed-halide lead perovskites powders (MA1-yCsyPb(BrnCl1-n)3) with emission spanning the green to blue region of the visible spectrum. Upon addition of amantadine hydrochloride, a strong enhancement in the PLQY can be obtained with only minor structural changes.