Organic cocrystal materials have considerable promise in areas as broad as luminescent materials, photoelectric transformation, photothermal (PT) conversion and pharmaceutical preparations. However, the development of highly efficient near-infrared (NIR) light PT conversion system remains extremely challenging. In this work, a new cocrystal with high efficiency of NIR PT conversion is constructed by using rapid self-assembly method based on small donor-acceptor organic molecules, N,N,N',N'-tetramethyl-p-phenylenediamine(TMPD) and pyromellitic dianhydride(PMDA). The TMPD-PMDA cocrystal has a widespread absorption from 200 nm to 1500 nm due to the intermolecular charge transfer. Via this cocrystal, we were able to improve the NIR PT efficiency from 18.8% 1 to 87.2%, thus significantly elevating the PT performance of NIR light systems. Ultrafast transient absorption studies reveal that the lifetime of the vibrational cooling and internal conversion processes are extraordinarily fast (about 0.12 ps) and their amplitude is up to 94.4%. The ultrafast and predominantly non-radiative excited state transition processes appear to account for the high NIR PT conversion efficiency. When using this cocrystal in a cocrystal-PTFE membrane system for water desalination using 808 nm light, the light-to-water evaporation efficiency reaches up to 59.1%. Furthermore, when the TMPD-PMDA cocrystal is doped into polydimethylsiloxane (PMDS) cubes, this cocrystal can be a potential excellent candidate for applications as a NIR PT therapy agent. This cocrystal advantages include simple preparation, highly efficient PT conversion and low cost and therefore may be suitable to develop for applications in the areas of NIR imaging, PT therapy and water desalination.