Chagarov Evgueni, Sardashti Kasra, Kummel Andrew C, Lee Yun Seog, Haight Richard, Gershon Talia S
Department of Chemistry and Biochemistry, University of California, 9500 Gilman Dr, La Jolla, San Diego, California 92093, USA.
IBM T.J. Watson Research Center, PO Box 218, Yorktown Hts., New York 10598, USA.
J Chem Phys. 2016 Mar 14;144(10):104704. doi: 10.1063/1.4943270.
The growth in efficiency of earth-abundant kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells has slowed, due in part to the intrinsic limitations imposed by the band tailing attributed primarily to I-II antisite exchange. In this study, density functional theory simulations show that when Ag is substituted for Cu to form kesterite Ag2ZnSnSe4 (AZTSe), the I-II isolated antisite formation energy becomes 3.7 times greater than in CZTSSe, resulting in at least an order of magnitude reduction in I-II antisite density. Experimental evidence of an optoelectronically improved material is also provided. Comparison of the low-temperature photoluminescence (PL) structure of Cu(In,Ga)Se2 (CIGSe), CZTSSe, and AZTSe shows that AZTSe has a shallow defect structure with emission significantly closer to the band edge than CZTSe. Existence of suppressed band tailing is found in the proximity of the room-temperature PL peak of AZTSe to its measured band gap. The results are consistent with AZTSe being a promising alternative to CZTSSe and CIGSe for thin film photovoltaics.
地球上储量丰富的铜锌锡硫硒（CZTSSe）太阳能电池的效率增长已经放缓，部分原因是主要归因于I-II反位交换的能带拖尾所带来的内在限制。在本研究中，密度泛函理论模拟表明，当用银取代铜形成硫硒铜锌锡矿Ag2ZnSnSe4（AZTSe）时，I-II孤立反位形成能比CZTSSe中的大3.7倍，导致I-II反位密度至少降低一个数量级。同时还提供了这种光电性能得到改善的材料的实验证据。对铜铟镓硒（CIGSe）、CZTSSe和AZTSe的低温光致发光（PL）结构的比较表明，AZTSe具有浅缺陷结构，其发射比CZTSe更接近带边。在AZTSe的室温PL峰与其测量带隙附近发现了能带拖尾受到抑制的情况。这些结果与AZTSe作为薄膜光伏领域中CZTSSe和CIGSe的有前景的替代材料是一致的。
