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[Display omitted] • High-quality PtSe 2 was synthesized on hBN using MBE. • PtSe 2 synthesized on hBN has higher crystallinity and less grain boundaries than that on SiO 2 /Si. • Fabricated a PtSe 2 -based photodetector on hBN shows a higher response to the illuminated light with a broadband wavelength. • The PtSe 2 -based photodetector fabricated on hBN shows higher photocurrent, faster response speed, and superior broadband detection range. Two-dimensional (2D) van der Waals materials are potential candidates for high-performance optoelectrical devices owing to the bandgap modulation, high on/off ratio, and ultra-stability. However, the challenge of synthesizing large-area, uniform, and high-quality 2D van der Waals materials should be addressed to manufacture large-scale and uniform optoelectrical devices using these materials. Although several previous studies investigated synthesis methods using chemical vapor deposition and molecular beam epitaxy (MBE), there are certain limitations such as the non-uniformity, lots of grain boundaries, and low carrier mobility. Here, by studying a method for synthesizing PtSe 2 on hBN buffer layer using MBE, we fabricated a PtSe 2 -based broadband photodetector. The high-quality PtSe 2 synthesized on hBN was evaluated using Raman spectroscopy and scanning transmission electron spectroscopy. These revealed that the synthesized PtSe 2 had a high quality and small grain boundary compared with PtSe 2 synthesized on SiO 2. Owing to the reduction in the carrier scattering and carrier recombination because of the high-quality and small grain boundaries, the photodetector using PtSe 2 synthesized on hBN displayed optoelectrical properties that were significantly better than those of PtSe 2 synthesized on SiO 2. Therefore, using hBN as a buffer layer for PtSe 2 growth, a remarkable performance of complex optoelectrical devices could be achieved. [ABSTRACT FROM AUTHOR]