BiFeO_(3)系固溶体钙钛矿窄禁带铁电半导体光伏材料  

Narrow bandgap ferroelectric semiconductors within BiFeO_(3)-based solid solution perovskites

作　　者：吴强 宁欢颇[1,2] 于剑 Qiang Wu;Huanpo Ning;Jian Yu(College of Science,Donghua University,Shanghai 201620,China;Institute of Functional Materials,Donghua University,Shanghai 201620,China)

机构地区：[1]东华大学理学院,上海201620 [2]东华大学功能材料研究中心,上海201620

出　　处：《科学通报》2021年第31期4045-4053,共9页Chinese Science Bulletin

基　　金：国家自然科学基金(61771122和11704065)资助。

摘　　要：铁电半导体能够单片式集成半导体p-n结光伏与铁电体光伏,有望突破太阳能光伏电池能量转换效率的Shockley-Queisser理论极限.本研究采用Mn^(4+)、Co^(2+)等磁性离子替代技术在BiFeO_(3)系固溶体钙钛矿中成功创制出一系列窄禁带室温铁电半导体,应用传统固相反应法制备了0.50BiFeO_(3)-0.25A_(1)MnO_(3)-0.25A_(2)TiO_(3)(A_(1)=Ca、Sr、Ba,A_(2)=Sr、Ba、Pb)和0.49BiFeO_(3)-0.26BaTiO_(3)-0.25(Sr_(1–x)Ba_(x))(Co_(1/3)Nb_(2/3))O_(3)单相钙钛矿陶瓷.室温拉曼散射光谱测试表明这些固溶体钙钛矿空间中心反演对称破缺,与应用Vegard规则估算它们是室温铁电相的结果一致.紫外-可见-近红外波段吸光度测试表明它们是禁带宽度E_(g)在0.75~1.0 eV的直接带隙半导体.变温电学测试表明其电阻率为~10^(6)Ωcm(40°C)量级、缺陷激活能E_(a)~0.5 eV.与卤化物钙钛矿相比,E_(g)~0.9 eV的BiFeO_(3)系固溶体钙钛矿对太阳能光谱的吸收已深入近红外波段.通过分析铁电半导体禁带宽度与磁性离子d电子组态、μ×r_(A)/r_(B)系综描述符(μ、r_(A)和r_(B)分别为原胞的约合质量、A位和B位离子半径)之间的因果关系,为下一步优选集成半导体p-n结光伏和铁电体光伏太阳能电池的功能元,提供了材料预测设计的物理模型.Solar energy is a clean and renewable source of energy.Various solar photovoltaic(PV)cell technologies have been developed,out of which perovskite PV cell technology is growing rapidly.Using organometal halide perovskite as an optical absorption component,the power conversion efficiency(PCE)of heterojunction solar PV cells increased from 3.8%in 2009 to 25.5%recently.Nonetheless,the bottleneck for CH_(3)NH_(3)PbI_(3)-based solar cells entering into commercial market is their poor stabilities relating to environmental,thermal,and ultraviolet light influence.In contrast,transition metal oxide perovskites are thermodynamically and chemically stable enough for solar cells’commercialization,with more advantages such as bandgap(E_(g))adjustability from 0 to 6 eV,processing being compatible with transparent conducting oxides,and ferroelectric bulk PV effect.Owing to a wide E_(g),traditional ferroelectric perovskite oxides exhibit poor visible optical absorption,low electrical conductivity,and thus extremely low PCE.As an alternative to p-n junction PV effect,ferroelectric bulk PV effect provides a new separation mechanism for photoexcited carriers,which is closely related to spatial inversion symmetry breaking and its resulting spontaneous electric polarization.Different from p-n junction,the active space for photo-excited carrier separation spans the whole ferroelectric body,and thus an above-E_(g) open-circuit voltage is produced.By narrowing E_(g) while maintaining ferroelectricity of oxide perovskites,ferroelectric semiconductors become available to monolithically integrate the p-n junction and ferroelectric bulk PV effects,which could,in principle,go beyond the Shockley-Queisser theoretical PCE limit of conventional p-n junction solar cells.Bismuth ferrite(BiFeO_(3))has been experimentally demonstrated to exhibit ferroelectric PV effect.Meanwhile,it has a high ferroelectric Curie temperature(T_(C))of 830°C and an intermediate E_(g) of~2.2 eV,providing a large chemical space for solid solution perovskite oxides to

关 键 词：氧化物钙钛矿 禁带宽度 铁电半导体 太阳能光伏材料 

分 类 号：TB34[一般工业技术—材料科学与工程] TM914.4[电气工程—电力电子与电力传动]