Light-emitting diodes (LEDs) have enabled critical functionality across various applications including solid-state lighting, displays, water purification, 3D printing, sensing, and more. Metal halide perovskite semiconductors are promising candidates for next-generation optoelectronic devices, including LEDs, due to their bandgap tunability, sharp color purity, and inexpensive processing. In this seminar, I will discuss progress towards optimizing the performance of emissive perovskite semiconductors in both the visible and ultraviolet (UV) spectrum. Focusing first on the visible spectrum, by replacing a portion of the lead with manganese and introducing tris(4-fluorophenyl)phosphine oxide (TFPPO) as an additive in organic-inorganic hybrid quasi-bulk perovskite thin films, we can achieve bright and efficient perovskite LEDs (PeLEDs). However, while the TFPPO additive boosts green Mn2+-doped PeLED efficiency, it also worsens its device stability. By utilizing repeated electrical scans and time-resolved photoluminescence measurements, we systematically study this efficiency-stability trade-off. Next, we employ emissive 2D lead halide perovskites to push light emission towards the UV spectrum. By engineering the films and corresponding device architectures, we can fabricate both 408 nm violet-emitting and 399 nm UV-emitting PeLEDs. Furthermore, to achieve deeper UV light emission, one must consider other materials beyond 2D lead halide perovskites. By investigating lead-free rare earth element-based perovskite materials, we show that cerium-based perovskite films can demonstrate 367 nm photoluminescent emission paving the way for deeper UV-emitting PeLEDs. Lastly, by combining organic spacer cations and europium halides, we showcase bright, lead-free perovskite nanoplatelets and enable new non-toxic pathways for both deep blue and violet light emission. Overall, these findings suggest that perovskite semiconductors show strong potential to revolutionize light-emitting technologies in both the visible and UV spectrums.