Synthesis, Structure, Band Gap, and Near-Infrared Photosensitivity of a New Chalcogenide Crystal, (NH4)4Ag12Sn7Se22

A new chalcogenide crystal, (NH4)4Ag12Sn7Se22 (FJSM-STS), has been solvothermally synthesized. The crystal structure, which is composed of arrays of [Sn3Se9]n6n− chains interconnecting [SnAg6Se10]n10n− and [Ag3Se4]n5n− layers, is unprecedented among the reported A/Ag/Sn/Q (A = cation; Q = S, Se, and Te) compounds. Optical absorption together with theoretical calculations of the band structure indicate a direct band gap of 1.21 eV for FJSM-STS, which is close to the ideal band gap to maximize the photoconversion efficiency proposed by Shockley and Queisser. The toxic-metal-free crystal of FJSM-STS exhibits obvious photosensitivity in the near-infrared range. The variates of power and temperature on the photosensitivity have been studied.一种新型硫系晶体(NH₄)₄Ag₁₂Sn₇Se₂₂（命名为FJSM-STS）已通过溶剂热法合成。该晶体的结构由[Sn₃Se₉]ₙ⁶ⁿ⁻链与[SnAg₆Se₁₀]ₙ¹⁰ⁿ⁻、[Ag₃Se₄]ₙ⁵ⁿ⁻层相互交联构成，在已报道的A/Ag/Sn/Q（A为阳离子；Q代表S、Se、Te硫族元素）类化合物中尚无先例。光吸收测试与能带结构理论计算结果表明，FJSM-STS的直接带隙为1.21 eV，该值接近肖克利与奎伊瑟提出的可最大化光电转换效率的理想带隙。这款无有毒金属的FJSM-STS晶体在近红外区间展现出显著的光敏性。本研究针对光功率与温度对其光敏性的影响开展了系统探究。