Morphology-Controlled Fully Spray-Coated Organic Solar Cells with High Power-to-Weight Ratio

Abstract

High power-to-weight photovoltaics are crucial for weight-constrained platforms, including near-Earth satellites, unmanned aerial systems, and portable power. Spray coating offers a particularly attractive deposition route due to its non-contact nature and substrate compatibility. It enables the direct formation of functional layers onto host surfaces with varied geometries, thereby minimizing, and in practice often effectively bypassing, the added mass a dedicated carrier substrate. However, spray-coated organic solar cells (OSCs) remain less mature than spin- or blade-coated counterparts because coupled atomization, droplet transport, wetting, and evaporation kinetics complicate morphology control. In this work, by systematically regulating film formation and active-layer morphology in the D18:L8BO:PYIT system, we achieve a record power conversion efficiency (PCE) of 18.27% for OSCs with a spray-coated active layer. In situ UV–visible spectroscopy combined with atomic force microscopy indicates that incorporating PYIT and applying solvent vapor annealing moderate assembly kinetics toward a more uniform pathway, yielding a refined, interconnected active-layer morphology. Based on this active layer design, fully spray-coated OSCs achieve a power-to-weight ratio exceeding 250 W g-1. Furthermore, AM0 simulations project a PCE of 17.56% for near -Earth orbit operation, with a power-to-weight ratio approaching 600 W g-1 and an annual energy yield of 1435.8 kWh m-2 year-1. This work highlights fully spray-coated fabrication combined with targeted morphology control as a promising route toward high power-to-weight OSCs.