A Eu3+-Eu2+ ion redox shuttle imparts operational durability to Pb-I perovskite solar cells
Authors: Ziqi Xu
Qi Chen
Yuan Huang
Huanping Zhou
Ligang Wang
Guanghaojie Zheng
Zheng Liu
Bolong Huang
Nengxu Li
Chun-Hua Yan
Ling-Dong Sun
Bowei Dong
Yihua Chen
Liang Li
Junnan Hu
Mingzi Sun
Journal: Science (2019)
Discipline: Multidisciplinary
Keywords: metal halide perovskite absorber; lead defects; iodine defects; europium ion pair; redox shuttle
Affiliations: Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry, Key Laboratory for the Physics and Chemistry of Nanodevices, Beijing Key Laboratory for Theory and Technology of Advanced Battery Materials, Department of Materials Science and Engineering, College of Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R. China., Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry, Key Laboratory for the Physics and Chemistry of Nanodevices, Beijing Key Laboratory for Theory and Technology of Advanced Battery Materials, Department of Materials Science and Engineering, College of Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R. China.   ., Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR., Department of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, P.R. China.

Abstract:  The components with soft nature in the metal halide perovskite absorber usually generate lead (Pb)0 and iodine (I)0 defects during device fabrication and operation. These defects serve as not only recombination centers to deteriorate device efficiency but also degradation initiators to hamper device lifetimes. We show that the europium ion pair Eu3+-Eu2+ acts as the "redox shuttle" that selectively oxidized Pb0 and reduced I0 defects simultaneously in a cyclical transition. The resultant device achieves a power conversion efficiency (PCE) of 21.52% (certified 20.52%) with substantially improved long-term durability. The devices retained 92% and 89% of the peak PCE under 1-sun continuous illumination or heating at 85°C for 1500 hours and 91% of the original stable PCE after maximum power point tracking for 500 hours, respectively. 

Retracted: No

PubPeer comments:
 This manuscript is quite problematic in my view: 1. How could it be possible to do the redox reaction for the whole perovskite film by doping (0.15 %) by Eu$3+$ ? The whole molar mass of perovskite film is way larger than this trace doping. The whole film degrades under operation, such a low dose of doping hardly can recover the whole film even if it is mobile in the whole film. But will 2. The characterization is quite confused. They show the results of two different components of perovskite. For the supporting information S9 and S10, they show perovskite film with different bandgaps for absorption spectrum and PL spectrum. In general, PL is more reliable. Thus, 790 nm peak cannot achieve current density which is higher than 23 mA cm$2$. 3. For fig 1E, it is hard to get Eu$3+$ peak for room temperature by EPR because of the broadening effect of peaks. g is not the proportionality factor, and it is called Landau factor. The peak should come from some other oxides. The width of the peak is less than 20G, it should be more than 100 G in the textbook. Only a low-temperature measurement would make sense for there purpose. ,