Room temperature phosphorescent (RTP) materials have always remained an active research area due to their potential utility in optoelectronic and biomedical applications. Recently, pure organic crystalline materials with RTP properties have quickly been shaping a new research direction in materials science and crystal engineering due to their inherent characteristics, i.e. low cost, toxicity, and environmental load in comparison to their organometallic counterparts. Despite the emerging demand, organic crystalline materials with efficient RTP are very limited in number since the phenomenon of RTP has traditionally been considered the research field of inorganic and organometallic materials. In this regard, the current challenge is to develop metal-free organic RTP materials and tune their emission efficiency via different novel design principles and synthetic approaches. In this proposal, noncovalent (mechanochemical) syntheses will be employed for the construction of new organic RTP materials via chalcogen and halogen bond driven cocrystal engineering. In addition, the RTP emission of crystalline materials will be improved and tuned by application of high pressure. Through precise engineering of supramolecular structures by cocrystal design and incorporation of heavy halogen and chalcogen atoms, with applying high pressure, a new class of functional organic RTP crystalline materials can be produced, which would be similarly efficient as their organometallic equivalents.