Wide-Band-Gap Mixed-Halide 3D Perovskites: Electronic Structure and Halide Segregation Investigation

Siyuan Zhang, Ming-Chun Tang, Nhan V. Nguyen, Thomas D. Anthopoulos, Christina A. Hacker

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Mixed-halide organolead perovskites (MAPbX3) are of great interest for both single-junction and tandem solar cells because of their wide band gap. In this study, we investigate the family of mixed iodide/bromide (I/Br) and bromide/chloride (Br/Cl) perovskites, revealing the strong influence of halide substitution on electronic properties, morphology, film composition, and phase segregation. A qualitative blue shift with the I → Br → Cl series was observed, with the resulting optical absorption ranging from 420 to 800 nm covering nearly the entire visible region. The ionization potential increases from ≈6.0 to ≈7.0 eV as the halide composition changes from I to Br. However, with Cl components, the valence band position shows little variation, while the conduction band minimum shifts to a lower value with increasing Cl concentration. By collecting XPS spectra as a function of the sputtering depth, we observed halide segregation in both I/Br and Br/Cl mixed-halide perovskite films, where the large halide ion (I in the I/Br mix or Br in the Br/Cl mix) is preferentially found on the surface of the film and the smaller halide ion (Br in the I/Br mix or Cl in the Br/Cl mix) accumulates at the bottom of the film. These differences in the band structure, electronic properties, morphology, and film composition impacted the device performance: a decreased short-circuit current density and increased open-circuit voltage were observed with the I → Br → Cl series. This study highlights the role of halides in the band structure and phase segregation in mixed-halide perovskite solar cells and provides a foundational framework for future optoelectronic applications of these materials.
Original languageEnglish (US)
JournalACS Applied Electronic Materials
DOIs
StatePublished - May 10 2021

Bibliographical note

KAUST Repository Item: Exported on 2021-06-11
Acknowledged KAUST grant number(s): OSR-2019-CRG8-4095.3, OSR2018-CARF/CCF-3079
Acknowledgements: This work was supported by the National Institute of Standards and Technology (NIST) Financial Assistance Award with Federal Award ID 70NANB16H228, and King Abdullah University of Science and Technology (KAUST), Office of Sponsored Research (OSR) under Award No: OSR2018-CARF/CCF-3079, and No: OSR-2019-CRG8-4095.3.

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