高热电优值新型Si-Ge基材料的能带调制、输运性质及性能研究

With the exacerbation of the crisis of energy and environment, the research of thermoelectric materials has drawn wide attention and made great progress along with the development of aerospace and microelectronics technologies. Theoretical and experimental studies show that Si-Ge based material is an irreplaceable preferred material in high temperature thermoelectric field, and has broad prospects in the applications in high temperature environment. This project innovatively puts forward that learn from research methods, technical approaches and research results which can effectively improve the photoelectric conversion efficiency in photovoltaic materials, systematically conducts the research of the inner relationship between the crystal structure and the electronic structure of the novel Si-Ge alloy, the action mechanism of the Seebeck coefficient and the thermal conductivity of phonons and electrons in the Si-Ge alloy with different structures and the method of obtain Si-Ge alloy modification and characterization technology as well as its low thermal conductivity and high thermoelectric figure of merit materials. Through solving the key scientific problems, such as the calculation of the new Si-Ge based material structure with high thermoelectric figure of merit which can be stably existed and the optimization of thermoelectric properties as well as thermoelectric figure of merit, it is expected to break through the theoretical and technological bottlenecks of the new Si-Ge material with high thermoelectric figure of merit, thus promoting the development of green energy and creating the conditions for the application of Si-Ge materials in thermoelectricity.

随着能源和环境危机的加剧，热电材料的研究引起了广泛关注并伴随着航天与微电子等技术的发展取得了长足的进步。理论与实验研究表明，Si-Ge基材料是高温热电的不可代替的首选材料，在空间开发和太空探测等高温环境应用方面前景广阔。本项目创新性的提出借鉴光电材料中有效提高光电转换效率的研究方法、技术途径和研究成果，系统开展新型Si-Ge合金晶体结构与电子结构之间内在关系、不同结构Si-Ge合金电子和声子对Seebeck系数和热导率作用机理、Si-Ge合金改性与表征技术及其低热导率高热电优值材料获得方法等的研究。通过对可稳定存在的新型高热电优值Si-Ge基材料结构计算、热电特性以及热电优值的优化等关键科学问题的解决，有望突破新型高热电优值Si-Ge材料的理论和技术瓶颈，从而推动绿色能源的发展并为Si-Ge材料在热电方面的应用创造条件。

随着能源和环境危机的加剧，热电材料的研究引起了广泛关注并伴随着航天与微电子等技术的发展取得了长足的进步。理论与实验研究表明，Si-Ge基材料是高温热电的不可代替的首选材料，在空间开发和太空探测等高温环境应用方面前景广阔。本项目创新性的提出借鉴光电材料中有效提高光电转换效率的研究方法、技术途径和研究成果，系统的设计了60余种新型硅锗合金及其他同族元素合金，系统开展新型Si-Ge合金晶体结构与电子结构之间内在关系，成功设计了十余种具有直接带隙的硅锗合金材料，例如，Cmca相中GeSn原子以1：1的比例混合，将间接带隙Cmca-Ge成功调制为直接带隙半导体材料；C2/c相中的Si24和Si16Ge8是准直接半导体合金，它们的间接带隙为1.523和1.346 eV，直接带隙为1.527和1.354 eV，而C2/c相中Si8Ge16和Ge24是带隙分别为1.160和1.102 eV的直接带隙半导体；P63/mmc相Si5Ge和Si4Ge2的直接带隙分别为0.63 eV和0.18 eV等重要结果。随后还研究了它们的光学性质，虽然Si6-xGex(x =0，1，2)的禁带宽度不在1.0和1.5之间，不能很好地吸收可见光，但是它们对红外光的吸收能力大于可见光。虽然Si5Ge和Si4Ge2对可见光的吸收能力略大于Si6，但前者对红外光的吸收能力明显高于后者在可见光范围内的吸收谱，进一步验证了新设计的稳定的Si-Ge合金晶体作为光电材料的潜在价值。此外，还研究了部分新型Si-Ge合金晶体的有效质量和迁移率等输运性质，研究发现C2/m相 Si8Ge8和Si4Ge12电子迁移率和空穴迁移率高达16527 cm2V-1s-1和3033 cm2V-1s-1，有望突破新型高热电优值Si-Ge材料的理论和技术瓶颈，从而推动绿色能源的发展并为Si-Ge材料在热电方面的应用创造条件。