Ethylenediammonium-Based "hollow" Pb/Sn Perovskites with Ideal Band Gap Yield Solar Cells with Higher Efficiency and Stability

Weijun Ke, Ioannis Spanopoulos, Qing Tu, Ido Hadar, Xiaotong Li, Gajendra S. Shekhawat, Vinayak P. Dravid, Mercouri G. Kanatzidis*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

95 Scopus citations

Abstract

The power conversion efficiency (PCE) of halide perovskite solar cells is now comparable to that of commercial solar cells. These solar cells are generally based on multication mixed-halide perovskite absorbers with nonideal band gaps of 1.5-1.6 eV. The PCE should be able to rise further if the solar cells could use narrower-band gap absorbers (1.2-1.4 eV). Reducing the Pb content of the semiconductors without sacrificing performance is also a significant driver in the perovskite solar cell research. Here, we demonstrate that mixed Pb/Sn-based perovskites containing the oversized ethylenediammonium (en) dication, {en}FA0.5MA0.5Sn0.5Pb0.5I3 (FA = formamidinium, MA = methylammonium), can exhibit ideal band gaps of 1.27-1.38 eV, suitable for the assembly of single-junction solar cells with higher efficiencies. The use of en dication creates a three-dimensional (3D) hollow inorganic perovskite structure, which was verified through crystal density measurements and single-crystal X-ray diffraction structural analysis as well as nuclear magnetic resonance measurements. The {en}FA0.5MA0.5Sn0.5Pb0.5I3 structure has massive Pb/Sn vacancies and much higher chemical stability than the same structure without en and vacancies. This new property reduces the dark current and carrier trap density and increases the carrier lifetime of the Pb/Sn-based perovskite films. Therefore, solar cells using {en}FA0.5MA0.5Sn0.5Pb0.5I3 light absorbers have substantially enhanced air stability and around 20% improvement in efficiency. After overlaying a thin MABr top layer, we found that the {5% en}FA0.5MA0.5Sn0.5Pb0.5I3 material gives an optimized PCE of 17.04%. The results highlight the strong promise of 3D hollow mixed Pb/Sn perovskites in achieving ideal band gap materials with higher chemical stability and lower Pb content for high-performance single-junction solar cells or multijunction solar cells serving as bottom cells.

Original languageEnglish (US)
Pages (from-to)8627-8637
Number of pages11
JournalJournal of the American Chemical Society
Volume141
Issue number21
DOIs
StatePublished - May 29 2019

Funding

This work was supported as part of the Center for Light Energy Activated Redox Processes (LEAP), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under award no. DESC0001059 (solar cell fabrication and characterization). Work in sample synthesis, processing, and structural characterization was supported by the Department of Energy, Office of Science grant SC0012541. PYSA measurements were carried out with equipment acquired by ONR grant N00014-18-1-2102. This work made use of the EPIC and SPID facility (NUANCE Center-Northwestern University), which have received support from the MRSEC program (NSF DMR-1720139) at the Materials Research Center, and the Nanoscale Science and Engineering Center (EEC-0118025/003), both programs of the National Science Foundation, the State of Illinois, and Northwestern University. This work was supported as part of the Center for Light Energy Activated Redox Processes (LEAP), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under award no. DE-SC0001059 (solar cell fabrication and characterization). Work in sample synthesis processing, and structural characterization was supported by the Department of Energy, Office of Science grant SC0012541. PYSA measurements were carried out with equipment acquired by ONR grant N00014-18-1-2102. This work made use of the EPIC and SPID facility (NUANCE Center-Northwestern University), which have received support from the MRSEC program (NSF DMR-1720139) at the Materials Research Center, and the Nanoscale Science and Engineering Center (EEC-0118025/003), both programs of the National Science Foundation, the State of Illinois, and Northwestern University.

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry

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