Morphology-controlled fully spray-coated organic solar cells with a 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 of a dedicated carrier substrate. However, spray-coated organic solar cells (OSCs) remain less mature than their 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 per m² per year. This work highlights fully spray-coated fabrication combined with targeted morphology control as a promising route toward high power-to-weight OSCs.