Printed Photovoltaic Modules on Solution-Coatable Ultra-Thin Substrates for Mechanically Imperceptible Energy-Harvesting in E-Textiles

Owing to the ultra-thin functional film thicknesses and intrinsically amorphous nature of emerging organic photovoltaics (OPV), they are well suited for integration into flexible/stretchable form-factors necessary to enable power-harvesting capabilities in e-textiles. To date, large scale demonstrations of such devices have primarily been on rigid glass or thick plastic substrates (>100 um), thereby limiting their conformal integration onto surfaces, a feature critical for their adoption into e-textiles. Recent reports of devices fabricated on ultra-thin (<5 um) substrates make use of intrinsically hard-to-scale chemical vapor deposition (CVD) or solution-coating methods employing high-temperature (>250C) imidization processes requiring a nitrogen-ambient environment. Herein, we report on a novel approach to prepare ultra-thin releasable polyester (PET) substrates in air-ambient conditions through a roll-to-roll compatible solution-coating process. Subsequently we demonstrate fabrication of fully-printed OPV modules on the substrates and their integration onto a high-strength (5kN/m tensile strength), light-weight (<15 g/m^2) composite fabric. Access to such coatable and ultra-thin substrates amenable to subsequent integration into e-textiles enables a platform not only suitable for energy-harvesting but any thin-film technology including displays, sensors, transceivers and compute elements.