Large-Area Bilayer Organic Solar Cells: Manipulating Interface and Morphology with Solvent Drenched Slot-Die Coating

Organic photovoltaics (OPVs) have emerged as a promising technology for renewable energy production. However, their stability and performance depend on the morphology and roughness of the interface between donor and acceptor layers. In this study, we investigated the transport properties and degradation mechanisms of inverted bilayer solar cells based on P3HT using dark current measurements and capacitance spectroscopy. Our study shows that the molecular orientation and intermixing of the donor and acceptor layers can be regulated using a solvent-drenching slot-die coating, leading to interfaces with varying levels of smoothness. We demonstrate that devices with smooth interfaces exhibit higher open-circuit voltages, lower radiative and non radiative losses, and lower defect densities than those with rough interfaces. Moreover, we reveal the role of tunnelling-enhanced recombination in limiting the device performance and stability. Our findings provide insights into the design and optimization of bilayer OPV devices with a high interface quality and low voltage loss.