Slot-Die-Coated Ternary Organic Photovoltaics for Indoor Light Recycling

Efficient organic photovoltaics (OPVs) based on slot-die-coated (SD) ternary blends were developed for low-intensity indoor light harvesting. For active layers processed in air and from eco-friendly solvents, our device performances (under 1 sun and low light intensity) are the highest reported values for fluoro-dithiophenyl-benzothiadiazole donor polymer-based OPVs. The N-annulated perylene diimide dimer acceptor was incorporated into a blend of donor polymer (FBT) and fullerene acceptor (PC61BM) to give ternary bulk heterojunction blends. SD ternary-based devices under 1 sun illumination showed enhanced power conversion efficiency (PCE) from 6.8 to 7.7%. We observed enhancement in the short-circuit current density and open-circuit voltage of the devices. Under low light intensity light-emitting device illumination (ca. 2000 lux), the ternary-based devices achieved a PCE of 14.0% and a maximum power density of 79 μW/cm2 compared to a PCE of 12.0% and a maximum power density of 68 μW/cm2 for binary-based devices. Under the same illumination conditions, the spin-coated (SC) devices showed a PCE of 15.5% and a maximum power density of 88 μW/cm2. Collectively, these results demonstrate the exceptional promise of a SD ternary blend system for indoor light harvesting and the need to optimize active layers based on industry-relevant coating approaches toward mini modules.