Products Cited in Publications Worldwide Work Function Tuning of ZnO Layer using π-Conjugated Amphiphilic Langmuir Monolayers for Inverted Organic Solar Cells

Work Function Tuning of ZnO Layer using π-Conjugated Amphiphilic Langmuir Monolayers for Inverted Organic Solar Cells

Gerase, Yisak Tsegazab; Xu, Zhuo; Dellith, Andrea; Dellith, Jan; Ryabchykov, Oleg; Bocklitz, Thomas; Schubert, Ulrich S; Hoppe, Harald; Presselt, Martin

DOI:

Abstract

Precise control over functional layers at the molecular level is essential for advancing high-performance optoelectronic devices. This study demonstrates a novel approach to tailoring the electronic and surface properties of zinc oxide (ZnO), a widely used electron transport layer (ETL), via the Langmuir-Schaefer (LS) technique. A linearly π-conjugated amphiphilic molecule, 4''-(pentyloxy)-1,1':4',1''-terphenyl-4-carboxylic acid (TPCA-PO), was employed to form highly ordered monolayers at the air–water interface. The molecular packing behavior was characterized using in-situ surface pressure–mean molecular area isotherms and Brewster Angle Microscopy (BAM), confirming the formation of densely packed Langmuir layers at the air-water interface. These layers were transferred onto ZnO layer by varying surface concentrations, resulting in a significant reduction of work function (up to 160 meV), attributed to interfacial dipole formation. Contact angle measurements further revealed increased surface hydrophobicity, suggesting improved stability under ambient conditions and enhanced compatibility with hydrophobic active layers. Although only marginal improvements in device performance were observed for PM6:Y6 inverted organic solar cells, the surface modifications highlight the potential of LS-based processing for energy level tuning and long-term stability enhancement in optoelectronic devices.

Keywords

work function ; interface ; Langmuir layer ; amphiphile ; surface concentration ; electron transport layer

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