Increased Electron Transport and Hole Blocking in an Aqueous Solution Processed Dye-Doped ZnO Cathode Interlayer for High Performance Organic Solar Cells

Abstract

In this work, we report high electron transport and hole blocking capability of hybrid photoconductive interlayer materials manufactured from an aqueous solution, which are achieved by doping perylene bisimide dyes into zinc oxide (ZnO) through the formation of ionic bonding between the organic dopants and the inorganic matrix. Benzenesulfonic acid functional groups are introduced to perylene bisimide dye molecules, which enhance the solubility of the dye molecules in water and form ionic bonds with zinc atoms during the fabrication of the hybrid thin films. The ionic bonding assisted molecular dispersion endows the hybrid thin film with full photoconductive properties, which improves electron transport by photoinduced electron transfer from organic dye molecules to the conduction band of ZnO. Especially, the hole blocking ability is also highly increased. Both increased electron transport and hole blocking are benefits to the charge selectivity of the cathode interlayer, which results in a high fill factor in organic solar cells. A power conversion efficiency of up to 15.4% is achieved on the basis of such an aqueous solution processed hybrid interlayer when using PM6:Y6 as the active layer. In addition, the optimized thermal annealing temperature for the fabrication of the hybrid thin film is as low as 150 °C, which is a benefit for the application of such photoconductive materials in flexible devices.

Recent progress in cathode interlayer materials for non‐fullerene organic solar cells

“…The final device demonstrates increased charge extraction and higher conductivity. Luo et al 198 explored the impact of chemical bonding between ZnO and benzene sulfonic acid. Thanks to the formation of hydrogen and covalent bonds, the new composites CIL exhibited higher conductivity and improved charge extraction properties (Figure 10C,D).…”

“…(D) J–V characteristics of the i‐organic solar cells with device configurations of ITO/ZnO (30 nm) or ZnO:PBI‐SO 3 H (30 nm)/ PM6:Y6 (100 nm)/MoO 3 (10 nm)/Al (100 nm) under 1000 W m −2 AM 1.5G illumination. Reproduced with permission: Copyright 2020, American Chemical Society 198 …”

Silicon Naphthalocyanine Tetraimides: Cathode Interlayer Materials for Highly Efficient Organic Solar Cells

“…Organic solar cells (OSCs) with the potential for low‐cost, light‐weight, and flexible devices have drawn extensive research in the past decade [1–5] . Comparing a variety of active layer materials with excellent performance, only a few excellent interface materials have been reported, especially cathode interlayers, even though such interlayers can effectively prevent charge recombination and enhance device performance [6–8] …”

Performance and Stability of Polymer : Nonfullerene Solar Cells with 100 °C‐Annealed Electron‐Collecting Combination Layers

“…[16][17][18] Most high-efficiency polymer : nonfullerene solar cells so far have been fabricated with an inverted-type device structure and further improvement was achieved by employing interlayers (interfacial layers) on metal oxide-based electron-collecting buffer layers (ECBLs). [19][20][21][22][23] For the metal oxide-based ECBLs, zinc oxide (ZnO) precursor routes were mostly employed because of suitable work function of ZnO ( � 4.3 eV) for electron collection and wet-coating process using precursor solutions at room temperature. [24][25][26][27] However, thermal annealing processes at high temperatures (up to 200°C) were applied for securing high electron mobility and good film quality.…”