High-Temperature Transparent Polymer Heater Based on n-Doped Poly(benzodifurandione).

Here we report high-performance all-polymer transparent heaters based on the air-stable n-doped polymer poly(benzodifurandione) (n-PBDF). Using a scalable ethanol-based ink and a single-step, post-treatment-free spray-coating process, the resulting films combine low sheet resistance (Rs ≈ 60 Ω sq.-1), high visible light transmittance (VLT > 80%), and low optical haze (<0.30%). The heaters reach steady-state temperatures above 180 °C at low DC voltages (<24 V) with rapid heating rates (>2.5 °C s-1). Measurements of the in-plane and cross-plane thermal conductivities reveal a pronounced thermal anisotropy (κx,y/κz ≈ (35 to 37)), with a high in-plane conductivity of ≈3.4 W m-1 K-1 that promotes uniform heating. A thermal model accounting for the Temperature Coefficient of Resistance (TCR) is applied to extract key heater parameters, revealing rapid, predictable thermal response times (t90% ≈ (90 to 150) s). The n-PBDF heaters retain >85% of their initial performance after 7 days of continuous operation and withstand 60 000 bending cycles (10 mm radius), demonstrating both robust operational stability and mechanical durability. Finally, we demonstrate practical utility by rapid deicing of surface frost on glass-substrate heaters cooled on dry ice (-78.5 °C), and by integrating heaters fabricated on flexible PET substrates into ski goggles and motorcycle visors to enable rapid, low-voltage defogging.