Chemical analysis of the interface in bulk-heterojunction solar cells by X-ray photoelectron spectroscopy depth profiling

Yan Busby, Emil J W List-Kratochvil, Jean-Jacques Pireaux

    Research output: Contribution to journalArticlepeer-review


    Despite the wide use of blends combining an organic p-type polymer and molecular fullerene-based electron acceptor, the proper characterization of such bulk heterojunction materials is still challenging. To highlight structure-to-function relations and improve the device performance, advanced tools and strategies need to be developed to characterize composition and interfaces with sufficient accuracy. In this work, high-resolution X-ray photoelectron spectroscopy (XPS) is combined with very low energy argon ion beam sputtering to perform a nondestructive depth profile chemical analysis on full Al/P3HT:PCBM/PEDOT:PSS/ITO (P3HT, poly(3-hexylthiophene); PCBM, [6,6]-phenyl-C61-butyric acid methyl ester; PEDOT, poly(3,4-ethylenedioxythiophene; PSS, polystyrenesulfonate; ITO, indium tin oxide) bulk-heterojunction solar cell device stacks. Key information, such as P3HT and PCBM composition profiles and Al-PCBM chemical bonding, are deduced in this basic device structure. The interface chemical analysis allows us to evidence, with unprecedented accuracy, the inhomogeneous distribution of PCBM, characterized by a strong segregation toward the top metal electrode. The chemical analysis highresolution spectra allows us to reconstruct P3HT/PCBM ratio through the active layer depth and correlate with the device deposition protocol and performance. Results evidence an inhomogeneous P3HT/PCBM ratio and poorly controllable PCBM migration, which possibly explains the limited light-to-power conversion efficiency in this basic device structure. The work illustrates the high potential of XPS depth profile analysis for studying such organic/inorganic device stacks.

    Translated title of the contributionAnalyse chimique des interface dans des cellules solaires à hétérojonction bulk par profilage XPS
    Original languageEnglish
    Pages (from-to)3842-3848
    Number of pages7
    JournalACS Applied Materials & Interfaces
    Issue number4
    Publication statusPublished - 1 Feb 2017


    • Bulk heterojunction
    • Chemical analysis
    • Depth profile
    • Low-energy ion beams
    • P3HT:PCBM
    • Solar cells
    • XPS


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