Most high-performance OPV devices, however, use fabrication methods that are only suitable for small-scale laboratory experiments, such as spin-coating, alongside controlled atmospheric conditions in gloveboxes for both fabrication and testing. [1][2][3][4]10] In addition, the halogenated and volatile solvent chloroform is commonly used, despite it not being industrially viable. This is due to adverse health and environmental effects, as well as poor compatibility with printing methods due to the low boiling point and high volatility. Thermal procedures such as hot casting and thermal annealing are also used to process and cure the photoactive layer, respectively, of such OPVs devices, [12] which introduces energy-intensive steps during the fabrication process. To facilitate the lab-to-fab transition, it is necessary to move high-performance systems to industry-compatible processing. Slot-Die Coating (SDC) has been identified as a viable coating technique due to its inherent scalability, compatibility with roll-to-roll manufacturing, and a much reduced material waste compared to spin-coating. [13] It is estimated that 95-98% of material is wasted using spin-coating methods. [14] In addition, SDC is effective for high throughput film formation on flexible substrates, while maintaining control over film thickness. [15] SDC has challenges in controlling drying rates which impact film morphology, [16] but offers opportunities for efficient layer-by-layer coating. [17] Increased effort has been put towards the construction of OPV devices using industrially compatible conditions, that is, OPV at scale. This is encouraging for commercialization, but performance gaps exist between engineered lab-scale devices and roll-processed modules. [13,[18][19][20] It is critical that when developing roll-to-roll compatible coated OPV devices, all layers must be considered in the stack, not just the organic photoactive layer, which is most often only investigated. Although reported by some, the SDC of all three critical OPV layers (hole transport layer HTL, electron transport ETL, photoactive layer) remains largely unexplored in the academic literature using NFAs. This has been presented by Baran and co-workers, [13] and it remains a challenge to prepare multilayer SDC OPVs with high efficiency. [21,22] Encouraging, Destouesse et al., have demonstrated roll-to-roll processed, ITO-free OPVs based on NFAs, in air, with 5% PCE. [23] For single-layer SDC OPVs we have reported PCEs upwards of 6%, [24][25][26] while PCEs upwards of 12% have been reached. [12,27,28] For two-and three-layer SDC
