Ag Incorporation with Controlled Grain Growth Enables 12.5% Efficient Kesterite Solar Cell with Open Circuit Voltage Reached 64.2% Shockley–Queisser Limit
Yuancai Gong, Ruichan Qiu, Chuanyou Niu, Junjie Fu, Erin Jedlicka, Rajiv Giridharagopal, Qiang Zhu, Yage Zhou, Weibo Yan, Shaotang Yu, Jingjing Jiang, Sixin Wu, David S. Ginger, Wei Huang, Hao Xin
Abstract
Abstract The large open‐circuit voltage deficit ( V oc,def ) is the key issue that limits kesterite (Cu 2 ZnSn(S,Se) 4 , [CZTSSe]) solar cell performance. Substitution of Cu + by larger ionic Ag + ((Ag,Cu) 2 ZnSn(S,Se) 4 , [ACZTSSe]) is one strategy to reduce Cu–Zn disorder and improve kesterite V oc . However, the so far reported ACZTSSe solar cell has not demonstrated lower V oc,def than the world record device, indicating that some intrinsic defect properties cannot be mitigated using current approaches. Here, incorporation of Ag into kesterite through a dimethyl sulfoxide (DMSO) solution that can facilitate direct phase transformation grain growth and produce a uniform and less defective kesterite absorber is reported. The same coordination chemistry of Ag + and Cu + in the DMSO solution results in the same reaction path of ACZTSSe to CZTSSe, resulting in significant suppression of Cu Zn defects, its defect cluster [2Cu Zn + Sn Zn ], and deep level defect Cu Sn . A champion device with an efficiency of 12.5% (active area efficiency 13.5% without antireflection coating) and a record low V oc,def (64.2% Shockley–Queisser limit) is achieved from ACZTSSe with 5% Ag content.