Structure-property relations in Ag-Bi-I compounds: potential Pb-free absorbers in solar cells
Structure-property relations in Ag-Bi-I compounds: potential Pb-free absorbers in solar cells
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DOI：
10.1039/c8ta11227d
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发表时间：
2019-03-14
影响因子：
11.9
通讯作者：
Shimakawa, Yuichi
中科院分区：
文献类型：
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作者：
Koedtruad, Anucha;Goto, Masato;Shimakawa, Yuichi
近年来，Ag-Bi-I系统作为太阳能电池吸收体的新兴材料引起了人们的极大关注。我们研究了单相组成，分析了详细的晶体结构，测量了光学和电学性质，并确定了结构-性能关系的Ag 2 - 3xBixI 2。富Ag组分（x = 0.45-0.48）可得到具有CdCl 2型菱面体结构的单相样品，而富Bi组分（x = 0.52-0.57）可稳定缺陷尖晶石型立方结构。菱面体和立方结构都由立方密堆积的I-离子亚晶格组成，并且Ag/Bi组成的微小差异导致不同的晶体结构。CdCl 2型菱面体和缺陷尖晶石型立方化合物都表现出具有适当带隙能量的半导体行为，这表明这两种材料都可能用作太阳能电池中的吸收剂。菱面体结构化合物具有较浅的价带能、较大的间接带隙能、较高的电导率和较低的活化能。不同的性能的结果，在缺陷结构的差异，额外的银占据在菱面体相和缺陷的八面体网站在立方相。
Recently, Ag-Bi-I system has attracted significant attention as an emergent material for absorbers in solar cells. We have investigated the single-phase compositions, analyzed the detailed crystal structures, measured optical and electronic properties, and determined the structure-property relations of Ag2-3xBixI2. Single-phase samples with CdCl2-type rhombohedral structures were obtained with Ag-rich compositions (x = 0.45-0.48), while defect-spinel-type cubic structures were stabilized with Bi-rich compositions (x = 0.52-0.57). Both the rhombohedral and cubic structures consisted of the cubic close-packed I-ion sublattices, and the small difference in the Ag/Bi composition resulted in distinct crystal structures. Both the CdCl2-type rhombohedral and defect-spinel-type cubic compounds exhibited semiconducting behavior with proper band gap energies, which indicates that both materials are potentially useful as absorbers in solar cells. The rhombohedral structure compounds have shallower valence band energies, larger indirect band gap energies, and higher electrical conductivity with lower activation energy than the cubic structure compounds. The distinct properties result from the difference in the defect structures, additional Ag occupation in the rhombohedral phase and deficiencies of the octahedral site in the cubic phase.