The sustainability of light-based technologies and the materials science underlying them are no longer separate questions. Solar conversion, photocatalysis, radiative cooling, low-power environmental and biomedical sensing, and the optical hardware emerging at the heart of AI accelerators rest on the same families of thin films, semiconductors, and nanostructures: materials that must absorb, emit, and route photons with high efficiency under realistic operating conditions. Their performance is increasingly judged not by isolated figures of merit but by the energy invested in fabrication, the dissipation incurred in operation, and the difficulty of recovery at end of life. This symposium convenes the materials communities working at this intersection — chalcogenide and oxide thin films, halide perovskites, two-dimensional semiconductors, plasmonic nanostructures, and electro-optic oxides — under a shared sustainability lens. Topics include nanomaterials for plasmonic and photothermal energy conversion, radiative cooling for buildings and electronics, perovskite emitters and modulators, metasurfaces for solar harvesting, photonic and plasmonic sensing for environmental and biomedical monitoring, photonic computing for energy-efficient AI, AI-driven materials discovery, operando nanoscale spectroscopy, and circular processing of chalcogenide and perovskite stacks. The objective is a sustained conversation between communities whose materials, modelling tools, and fabrication routes are already converging.