Diphenyl selenide is primarily used in organic synthesis as a reagent or catalyst. It plays a role in the formation of carbon-selenium bonds, which are valuable in various chemical reactions, including the synthesis of organoselenium compounds. These compounds are useful in materials science, particularly in the development of semiconductors and photovoltaic materials. Additionally, diphenyl selenide is employed in the preparation of selenium-containing polymers, which exhibit unique properties like thermal stability and electrical conductivity. It also finds application in medicinal chemistry for the synthesis of selenium-based drugs, which are explored for their antioxidant and anticancer properties.