The replacement of a small amount of organic cations with bulkier organic spacer cations in the perovskite precursor solution to form a 2D perovskite passivation agent (2D-PPA) in 3D perovskite thin films has recently become a promising strategy for developing perovskite solar cells (PSCs) with long-term stability and high efficiency. However, the long, bulky organic cations often form a barrier, hindering charge transport. Herein, for the first time, 2D-PPA engineering based on wide-bandgap (≈1.68 eV) perovskites are reported. Pentafluorophenethylammonium (F5PEA+) is introduced to partially replace phenylethylammonium (PEA+) as the 2D-PPA, forming a strong noncovalent interaction between the two bulky cations. The charge transport across and within the planes of pure 2D perovskites, based on mixed ammoniums, increases by a factor of five and three compared with that of mono-cation 2D perovskites, respectively. The perovskite films based on mixed-ammonium (F5PEA+-PEA+) 2D-PPA exhibit similar surface morphology and crystal structure, but longer carrier lifetime, lower exciton binding energy, less trap density and higher conductivity, in comparison with those using mono-cation (PEA+) 2D-PPA. The performance of PSCs based on mixed-cation 2D-PPA is enhanced from 19.58% to 21.10% along with improved stability, which is the highest performance for reported wide-bandgap PSCs.
Bibliographical noteFunding Information:
This work was supported by the U.S. Department of Energy under contract no. DE-AC36-08GO28308 with Alliance for Sustainable Energy, Limited Liability Company (LLC), the Manager and Operator of the National Renewable Energy Laboratory. The authors thank the support on the design and characterization of F5PEAI-based perovskite materials from the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE), an Energy Frontier Research Center funded by the Office of Basic Energy Sciences, Office of Science within the U.S. Department of Energy. The authors also thank the support for PV device fabrication and characterization from the De-risking Halide Perovskite Solar Cells program, funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Solar Energy Technologies Office. J.Y.Y. thanks for the support from U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program. D.H.K. thanks for the support from the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (2019R1F1A1064095).
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- charge transports
- passivation agents
- solar cells
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering