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Hybrid organic-inorganic perovskites (HOIPs) are attracting significant attention as new semiconductor materials, due to their inherent tunability by varying both the organic and the inorganic components. However, keeping track of the dramatically increasing volume of materials data related to HOIPs is challenging. We here present an open database, "HybriD³" (Design, discovery and dissemination (D³) of data related to hybrid materials, https://materials.hybrid3.duke.edu), aiming to collect, curate, and make available materials data related to HOIPs. The database is open to the community and designed to accept community input for a broad set of data, i.e., experimental and computational, related to in principle any materials property. We demonstrate the use of the database for the widely investigated material pheneythylamine lead iodide, (PEA)₂PbI₄, for which several crystal structure refinements have been reported in past work. Using density functional theory including van der Waals effects, we identify the lowest-energy structure among them and provide the electronic band structure at a high level of theory (hybrid density functional theory including spin-orbit coupling).