Highly robust anode interlayer for water-proof and stretchable organic solar cells

Organic solar cells exhibit unique advantages over traditional rigid solar technologies in fabricating stretchable devices, making them an appealing portable energy solution for wearable electronics. However, few organic semiconductors simultaneously achieve both high optoelectronic performance and mechanical robustness, compromising the efficiency and durability of stretchable OSCs. Herein, we utilized the strong electrostatic interaction between ammonium groups and polyoxometalate (POM) to construct a cross-linked conjugated polyelectrolyte (CPE)-POM anode interlayer (AIL), namely PTN-POM, for OSCs. The PTN-POM film not only shows an electrical conductivity as high as 3.30×10⁻³ S/m, but also possesses a high stretchability, significantly outperforming the classic PEDOT:PSS AIL in terms of mechanical strength. The binary OSC modified by PTN-POM exhibits a PCE of 19.59%, which is the highest PCE for OSCs using a cross-linked AIL. Notably, by employing PTN-POM as AIL, a water-proof OSC could be fabricated, exhibiting no performance degradation after storage underwater for 42 days. Furthermore, the mechanical robustness of stretchable OSC has been significantly enhanced by incorporating PTN-POM, showing a PCE retention up to 81% under a large tensile strain of 50%. By developing a highly robust cross-linked AIL, this work significantly enhances the photovoltaic, waterproof, and mechanical properties of OSCs and helps promote wearable photovoltaics.