Lead halide perovskite solar cells have made enormous progress over the past decade, and record power conversion efficiencies are now exceeding those of established silicon technologies. In addition, lead halide perovskites are finding applications in other optoelectronic applications, such as LEDs and sensors. However, the toxicity of lead (Pb) is a formidable hurdle towards commercializing lead halide perovskites. A host of Pb-free perovskite materials are being developed as less toxic alternatives. These materials replace Pb with other metals such as tin, bismuth, and germanium. In this chapter we discuss the material and optoelectronic properties of Pb-free perovskite materials and their performance in solar cells, LEDs, memristors, and various detectors. Despite promising properties, many of these materials still need big advances in terms of stability and performance. Key to achieving properties on par with Pb-based perovskites will be a continued research effort into controlling the deposition of these materials and an intricate understanding of material properties, which will allow targeted improvement strategies.