All slot-die coated organic solar cells using an amine processed cathode interlayer based upon an amino acid functionalised perylene bisimide

Abstract

Green solution-processable organic photovoltaic cells (OPVs) have the potential to provide low-cost, clean, and accessible electricity. However, there are few organic materials that are compatible with multi-layer film formatting from halogen-free solvents using scalable coating methods. Current research focuses on devices using tin oxide (SnO₂). However, SnO₂ has surface traps and requires a passivating layer to maximise performance. Therefore, it is crucial to develop electron deficient organic materials that can passivate metal oxides to achieve maximum device performance. Rendering these materials and films solvent resistance is thus a major goal. Herein, we show that SnO₂ modified with a tyrosine appended perylene bisimide (PBI-Y) can be applied as an electron transport interlayer in PM6/Y6C12-based organic photovoltaic cells using an amine-based ink formulation. The SnO₂/PBI-Y films are characterised by optical absorption spectroscopy and atomic force microscopy and exhibit solvent resistance. The electrical characterisation shows that a PBI modification improves the conductivity of the SnO₂. Spin-coated devices show a power conversion efficiency (PCE) of 13%, among the best for all air-processed SnO₂-based OPVs. Fully slot-die coated devices achieve PCEs of 10%, demonstrating the potential for scale-up. This work opens a viable and sustainable method to develop organic photovoltaic devices using more environmentally friendly processing conditions.