The fabrication of organic solar cells on paper substrate is attractive as it paves the way for roll‐to‐roll‐processed modules on more ecologically friendly substrates. A paper‐substrate solar‐cell process is successfully demonstrated. Commercially available paper with coatings from the polyvinyl family of materials is made suitable for electronic‐device fabrication. Smoothing layers of polyvinyl formal (PVF) with a knife‐edge coater give them an acceptable root mean square roughness of around 2.6 ± 0.2 nm. This paper is shown to be compatible with subsequent organic‐solar‐cell device fabrication with a variety of solvents including polar solvents. Top‐illuminated solar cells with blends of either poly(3‐hexylthiophene) and [6,6]‐phenyl C61 butyric acid methyl ester (PCBM), or poly({4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl}{3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl}) and PCBM as photoactive layer having power conversion efficiencies up to 3.37% and 6.44%, respectively, are fabricated. A statistically significant number solar cells with different areas from multiple runs are fabricated and their solar cell parameters are analyzed and discussed. The results show strong promise for solar‐cell fabrication on environmentally friendly paper substrates.

The recent advent of the new class of organic molecules, the so-called non-fullerene acceptors, has resulted in skyrocketing power conversion efficiencies of organic solar cells. However, rapid degradation occurs under illumination, particularly when photocatalytic metal oxide electron transport layers are used in these devices. We introduced vitamin C (ascorbic acid) into the organic solar cells as a photostabilizer and systematically studied its photostabilizing effect on inverted PBDB-T:IT-4F devices. The presence of vitamin C as an antioxidant layer between the ZnO electron transport layer and the photoactive layer strongly suppressed the photocatalytic effect of ZnO that induces NFA photodegradation. Upon 96 h of exposure to AM 1.5G 1 Sun irradiation, the reference devices lost 64% of their initial efficiency, while those containing vitamin C lost only 38%. The UV−visible absorption, impedance spectroscopy, and light-dependent voltage and current measurements reveal that vitamin C reduces the photobleaching of NFA molecules and suppresses the charge recombination. This simple approach using a low-cost, naturally occurring antioxidant, provides an efficient strategy for improving photostability of organic semiconductor-based devices.