基于四面体网络结构的新型窄带隙铁电光伏材料的探索

Traditional ferroelectric materials process extremely large band gap (Eg) which leads to the poor absorption of the sun's rays and limited the application in the solar cell. Up to now, the ferroelectric materials with narrow Eg and high PV performance are really scarce. In early 2013, we have reported the first multiferroic compound KBiFe2O5 with narrow band gap (Eg=1.59eV), which exhibits excellent PV performance (Jsc~15 μA/cm2, Voc~8.8 V). The reduced Eg of KBiFe2O5 can be attributed to the FeO4 tetrahedral framework, which realizes the absorption of the visible and near-infrared light. The well-known multiferroics BiFeO3, whose PV performance is too poor to practical application, is constructed by FeO6 octahedral framework with a Eg=2.67 eV. Thus, it is urgent to explore new ferroelectric photovoltaic materials with narrow Eg and high PV performance. In this proposal, the research work will be focused on the preparation of new ferroelectric oxides with narrow Eg by constructing the tetrahedral network structure, as well as the assembly of the device for in-depth study on the PV performance. The specific studies including: the synthesis of AA′BB′O5 type new ferroelectrics with narrow Eg and excelllent PV performance by mild solution route; the preparation of high quality ferroelectric films by Magnetron sputtering and PLD technologies, and composite films with high conductive materials (grapheme or Ag nanoparticles) for improving PV performance; to explore other Bi, Pb-doped new ferroelectric materials with tetrahedral network structure and narrow Eg.

传统铁电材料禁带宽，受限于极低的太阳光吸收而无法应用于光伏。窄禁带的高性能铁电材料稀缺，申请者于2013年初发表了首个窄禁带(Eg=1.59eV)的多铁新氧化物(KBiFe2O5)，光电转换性能突出(Jsc=15μA/cm2, Voc=8.8V)。该晶体结构中四面体网络结构降低Eg，实现了可见和近红外光吸收。著名多铁材料BiFeO3具有八面体网络(Eg=2.67eV)，光伏效应不佳而无法实用，因此急需探索更高性能的新型铁电光伏材料。本项目将围绕构建四面体网络结构，制备出具有窄禁带的新型铁电氧化物，通过器件组装深入研究其光电转换性能。开展如下研究：液相法制备AA′BB′O5型铁电新化合物；制备KBiFe2O5与石墨烯、银纳米颗粒复合异质结构薄膜； Bi、Pb掺杂的具有四面体网络结构的窄带隙新型铁电材料。

到目前为止，具有可见光吸收的铁电光伏材料还比较稀缺且光伏性能均不佳，亟需探索光伏性能优异的新型窄带隙铁电材料。我们之前通过调控中心离子配位场的思路，成果制备了一种具有四面体配位结构的新型窄带隙铁电光伏材KBiFe2O5，该晶体结构中四面体网络结构降低Eg，实现了可见和近红外光吸收。因此，我们提出围绕构建四面体网络结构，制备出具有窄禁带的新型铁电氧化物，通过器件组装深入研究其光电性能。通过本项目的实施，已取得的重要结果有：1、通过离子掺杂方式制备了多种AA′BB′O5型铁电新化合物，拓展了该体系的种类；2、通过磁控溅射制备了KBiFe2O5薄膜，并且通过复合Ag纳米颗粒有效提升了薄膜的光电性能。此外，我们还利用DAC高压技术探索了KBiFe2O5薄膜材料的光电性能，并且得到了一种新的铁电相，该铁电相的剩余极化和光生电流比常压KBiFe2O5样品均有4倍以上的提升，此工作为有效提升铁电性半导体的光伏性能开辟了一条新途径；3、通过Bi、Pb离子掺杂制备了多种具有四面体网络结构的新型窄带隙材料，并且通过引入氧空位的方式来增强传统铁电材料的光吸收，为铁电光伏材料研究提供了新的实验依据和理论模型。