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The chalcohalide compound Hg3Se2I2 with a defect anti-perovskite structure has been demonstrated to be a promising semiconductor for room temperature X- and γ-ray detection. In this work, we use transport agents during the vapor growth of Hg3Se2I2 crystals under gradient temperature profiles to dramatically improve the size and yield of Hg3Se2I2 single crystals. Various growth conditions with combinations of organic polymer (polyethylene) with elemental Hg, Se, or I2 are compared. The largest single crystals (with size up to 7 × 5 × 3.5 mm3) were obtained using both polyethylene and excess I2 as the transport agents. The as-prepared detector devices based on these crystals have excellent photo response to a series of radiation sources, including low flux X-ray source, alpha particles, and γ-rays. The X-ray induced photocurrent of Hg3Se2I2 detectors is 3 orders of magnitude higher than the dark current, indicating excellent X-ray photosensitivity. Under 241Am α particle source (5.5 MeV), the best energy resolution obtained is ∼8.1%. The Hg3Se2I2 device also shows improved detector performance under 57Co and 137Cs γ-ray sources. The improved crystal growth and detector performance using this polymer additive during the vapor transport process further confirms the great potential for the development of Hg3Se2I2 for radiation detection.
