Efficient Hybrid Mixed Ion Perovskite Photovoltaics: In Situ Diagnostics of the Roles of Cesium and Potassium Alkali Cation Addition
Dang, Hoang X.
Nguyen, Nhan V.
Heilweil, Edwin J.
Hacker, Christina A.
Anthopoulos, Thomas D.
KAUST DepartmentAcademic Affairs
KAUST Solar Center (KSC)
Material Science and Engineering
Material Science and Engineering Program
Office of the VP
Organic Electronics and Photovoltaics Group
Physical Science and Engineering (PSE) Division
KAUST Grant NumberOSR-2018-CARF/CCF-3079
Online Publication Date2020-07-06
Print Publication Date2020-09
Permanent link to this recordhttp://hdl.handle.net/10754/663877
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AbstractPerovskite photovoltaics have made extraordinary progress in power conversion efficiency (PCE) and stability owing to process and formulation development. Perovskite cell performance benefits from the addition of alkali metal cations, such as cesium (Cs+) and potassium (K+) in mixed ion systems, but the underlying reasons are not fully understood. Here, we study the solidification of perovskite layers incorporating 5, 10, to 20% of Cs+ and K+ using in situ grazing incidence wide-angle X-ray scattering. We found that K+-doped solutions yield non-perovskite 4H phase rather than the 3C perovskite phase. For Cs+-doped formulations, both 4H and 3C phases are present at 5% Cs+, while the 3C perovskite phase forms in 10% Cs+-doped formulations, with undesirable halide segregation occurring at 20% Cs+. Post-deposition thermal annealing converts the intermediate 4H phase to the desirable 3C perovskite phase. Importantly, perovskite layers containing 5% of Cs+ or K+ exhibit reduced concentration of trap states, enhanced carrier mobility and lifetime. By carefully adjusting the Cs+ or K+ concentration to 5%, we demonstrate perovskite cells with a ≈5% higher average PCE than cells utilizing a higher cation concentrations. The study provides unique insights into the crystallization pathways towards perovskite phase engineering and improved cell performance.
CitationTang, M.-C., Fan, Y., Barrit, D., Li, R., Dang, H. X., Zhang, S., … Anthopoulos, T. D. (2020). Efficient Hybrid Mixed Ion Perovskite Photovoltaics: In Situ Diagnostics of the Roles of Cesium and Potassium Alkali Cation Addition. Solar RRL. doi:10.1002/solr.202000272
SponsorsThe work was supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No: OSR-2018-CARF/CCF-3079, and the National Key Research and Development Program of China (2017YFA0204800, 2016YFA0202403), National Natural Science Foundation of China (61604092, 61674098), National University Research Fund (Grant Nos. GK261001009, GK201603055), the 111 Project (B14041), the National 1000 Talents Plan program (1110010341). GIWAXS measurements were performed at the D-line at the Cornell High Energy Synchrotron Source (CHESS) at Cornell University. CHESS is supported by the NSF and NIH/NIGMS via NSF Award DMR-1332208. Dr. Tang acknowledges support under the Cooperative Research Agreement between the University of Maryland and the National Institute of Standards and Technology Physical Measurement Laboratory, Award 70NANB14H209, through the University of Maryland. All the commercial instruments and materials mentioned here are identified to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.