On the Paramount Role of Absorber Stoichiometry in (Ag,Cu)(In,Ga)Se 2 Wide‐Gap Solar Cells
On the Paramount Role of Absorber Stoichiometry in (Ag,Cu)(In,Ga)Se
2
Wide‐Gap Solar Cells
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吸收剂化学计量在 (Ag,Cu)(In,Ga)Se 2 宽禁带太阳能电池中的重要作用
DOI：
10.1002/solr.202000508
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发表时间：
2020
影响因子：
2.7
通讯作者：
M. Edoff
中科院分区：
文献类型：
--
作者：
J. Keller;L. Stolt;K. Sopiha;J. Larsen;L. Riekehr;M. Edoff
本文对宽禁带(Ag，Cu)(In，Ga)Se_2(ACIGS)太阳电池中吸收体非化学计量比效应进行了评价。结果表明，随着Ga、Ag含量的增加，ACIGS薄膜有形成有序空位化合物(OVCs)的趋势。对于给出1)串联器件中的顶部单元的最佳带隙(EG= 1.6-1.7 EV)以及同时2)与CDS缓冲层的良好的带对齐的所需特性的吸收体组合物，检测到对非化学计量比的极小容差。在这里，发现大量的富In或富Ga的OVC斑块形成于I组贫化的ACIGS。因此，相应的太阳能电池中的载流子传输和电荷收集显著受阻。传输障碍似乎随着储存时间的延长而增加，这对宽禁带ACIGS太阳能电池的长期稳定性提出了质疑。此外，Ga和Ag含量很高的样品的效率取决于电压扫描方向。结果表明，这种磁滞行为是由于1：1：2吸收体晶格中可移动的Na离子在偏压作用下发生重新分布所致。最后，对ACIGS系统中OVC的形成提供了更广阔的前景，并讨论了宽禁带ACIGS太阳电池的基本限制。
This contribution evaluates the effect of absorber off‐stoichiometry in wide‐gap (Ag,Cu)(In,Ga)Se2(ACIGS) solar cells. It is found that ACIGS films show an increased tendency to form ordered vacancy compounds (OVCs) with increasing Ga and Ag contents. Very little tolerance to off‐stoichiometry is detected for absorber compositions giving the desired properties of 1) an optimum bandgap (EG) for a top cell in tandem devices (EG= 1.6–1.7 eV) and at the same time 2) a favorable band alignment with a CdS buffer layer. Herein, massive formation of either In‐ or Ga‐enriched OVC patches is found for group I‐poor ACIGS. As a consequence, carrier transport and charge collection are significantly impeded in corresponding solar cells. The transport barrier appears to be increasing with storage time, questioning the long‐term stability of wide‐gap ACIGS solar cells. Furthermore, the efficiency of samples with very high Ga and Ag contents depends on the voltage sweep direction. It is proposed that the hysteresis behavior is caused by a redistribution of mobile Na ions in the 1:1:2 absorber lattice upon voltage bias. Finally, a broader perspective on OVC formation in the ACIGS system is provided and fundamental limitations for wide‐gap ACIGS solar cells are discussed.