Recycled or Bio-Based Solvents for the Synthesis of ZnO Nanoparticles: Characterization and Validation in Organic Solar Cells

TL;DR

This paper explores using recycled or bio-based solvents to make ZnO nanoparticles for solar cells, achieving similar performance to traditional methods.

Contribution

The study introduces sustainable solvents (recycled methanol and bioethanol) for ZnO NP synthesis without compromising solar cell efficiency.

Findings

ZnO nanoparticles synthesized with recycled methanol and bioethanol showed comparable optical and electronic properties to conventional methods.

Solar cells using these sustainable ZnO NPs achieved power conversion efficiencies of approximately 7%.

The alternative solvents validated a more eco-friendly approach without sacrificing performance.

Abstract

Among solution-processable metal oxides, zinc oxide (ZnO) nanoparticle inks are widely used in inverted organic solar cells for the preparation, at relatively low temperatures (<120 °C), of highly efficient electron-transporting layers. There is, however, a recent interest to develop more sustainable and less impacting methods/strategies for the preparation of ZnO NPs with controlled properties and improved performance. To this end, we report here the synthesis and characterization of ZnO NPs obtained using alternative reaction solvents derived from renewable or recycled sources. In detail, we use (i) recycled methanol (r-MeOH) to close the loop and minimize wastes or (ii) bioethanol (b-EtOH) to prove the effectiveness of a bio-based solvent. The effect of r-MeOH and b-EtOH on the optical, morphological, and electronic properties of the resulting ZnO NPs, both in solution and thin-films, is investigated, discussed, and compared to an analogous reference material. Moreover, to validate the properties of the resulting materials, we have prepared PTB7:PC71BM-based solar cells containing the different ZnO NPs as a cathode interlayer. Power conversion efficiencies comparable to the reference system (≈7%) were obtained, validating the proposed alternative and more sustainable approach.

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