基于胶体墨水技术的铜铟硒基薄膜多组分反应调控与成相机理研究

Copper Indium Selenium based thin films, typically CuInSe2 and Cu(In,Ga)Se2 , are leading candidates as light-absorbing semiconductors for thin film solar cells due to their unique combination of optical and electric properties, such as high solar energy conversion efficiency, distinguished radiation stability and long-term excitation stability. Recently,there have been increasing interesting in developing non-vacuum, solution based methods to fabricate thin film solar cells in order to decrease the fabrication cost and deposite on flexible substrates easily,in which an ink-coating technique has been proposed.However, many basic scientific issues such as passivation of nanocrystals surface, preparation of large columnar grain, densification of thin films and control of chemical ingredient fluctuation exist in prepared Copper Indium Selenium based thin films using the ink-coating technique.Therefore, this program presents an approch using binary and ternary precursor such as Cu-Se, In-Se, Ga-Se and In-Ga-Se nanocrystals to deposite multilayer ink-coated thin films which is in order to synthesize Copper Indium Selenium based thin films with high quality by utilizing inhomogeneous composition to active the thermal diffusion, and making use of low transient non-equilibrium phase with low melting point to accelerate the nanocrystalline growth. Meanwhile, the research about the scientific issues such as solution synthesis of nanocrystals, passivation of nanocrystals surface, mechanism of crystalline growth, path of chalcopyrite formation and control of chemical ingredient fluctuation is meaningful to prepare Copper Indium Selenium based thin films with high efficiency and low cost。

铜铟硒基(CuInSe2和CuInGaSe2等)薄膜太阳电池具有高的光电转换效率、优越的抗辐射性能和无光致衰减等优点，是最有希望的第二代光伏电池之一。近年来，胶体墨水沉积技术由于具有非真空、低成本、且易在柔性衬底上沉积等特点，成为了国内外研究的热点。然而，使用该技术在制备铜铟硒基薄膜时存在一些关键问题需要解决，比如纳米晶表面态钝化、柱状大晶粒的制备、薄膜的致密化和化学成分梯度控制等。因此，本项目拟采用溶液化学工艺制备亚二元（Cu-Se、In-Se、Ga-Se等）和亚三元(In-Ga-Se）纳米晶前驱体，进行多层异相墨水薄膜沉积，以期利用非均组成分布激活热扩散和暂态非平衡低熔相促进纳米晶生长，制备出高质量的铜铟硒基薄膜光吸收层。同时，研究纳米晶的液相法合成、表面态的钝化、晶体生长机制、黄铜矿的成相路径以及化学成分梯度的影响，为制备高效廉价的铜铟硒基光伏器件奠定了基础。

本项目主要围绕着非真空纳米晶胶体墨水法制备铜铟硒基薄膜的技术展开了研究。在项目期间，重点完成了以下几方面的研究工作：1. 发展了绿色、低毒、低成本的多元醇热注入法合成多种硒化物纳米晶，如亚二元的Cu2-xSe纳米片，CuSe纳米片，In2Se3纳米颗粒和Sb2Se3纳米棒，三元的CuInS2纳米粒子、CuInSe2纳米粒子和四元CuIn(S,Se)2纳米晶，有效调控了上述硒化物纳米材料的物相结构、形貌尺寸、化学计量比和分散性。研究了多元醇体系下影响纳米晶成核和生长的动力学和热力学因素，并对该体系下纳米材料的生长机制有了新的认识。同时，成功将多元醇热注入工艺推广到其它硒化物光电材料，典型如Sb2Se3纳米棒，获得了较优异的光电性能。2.开发了绿色、低成本的乙醇做为纳米晶的分散溶剂，采用简单的浸渍-提拉工艺结合后期的硒化热处理工艺，可制备出纯相、黄铜矿结构的铜铟硒基薄膜。项目研究了均相三元CuInS2和CuInSe2纳米晶硒化工艺和异相二元CuSe纳米晶和In2Se3纳米晶复合薄膜的硒化过程，结果表明，无论是均相三元纳米晶还是非均相二元纳米晶复合薄膜，在硒化热处理后薄膜晶粒均有所增长，致密性都有提高。同时明确了多相纳米晶薄膜热处理过程中，黄铜矿结构铜铟硒基薄膜的物相结构和形貌的演变机制。3、针对纳米晶墨水技术中C杂质的引入是难以避免的问题，发展了新颖的非真空巯-胺全溶液墨水沉积技术，采用乙二胺和乙二硫醇/巯基乙醇做为溶剂，成功溶解单质Cu，In，S和Se粉，避免了薄膜中C的残留，经硒化退火热处理后制备出了大晶粒尺寸、高致密且光电性质优良的铜铟硒基光吸收层薄膜材料，组装的太阳能电池获得了6.2%的光电转换效率。本项目的研究意义在于为将来开发大规模、低成本的非真空溶液技术制备高质量的铜铟硒基光吸收层薄膜打下了坚实的理论基础，并具有较强的实践指导意义。