Bioinspired sticker-type multilayer anti-reflective film for flexible perovskite solar cells

Abstract

Perovskite solar cells (PSCs) have been receiving attention for photovoltaic advantages of high-power conversion efficiency, cost-effectiveness, and easy fabrication process. Particularly, flexible PSCs (FPSCs) are considered to be promising renewable power sources due to the positive potential of flexible and lightweight properties. However, FPSCs tend to have lower efficiency compared to glass-based rigid PSCs (RPSCs). The main issue is high refractive index of polymer substrates such as polyethylene naphthalate (PEN), used for FPSCs, thereby reducing the external light absorption efficiency. In this study, we developed glasswing inspired sticker-type multilayer anti-reflective (GSMA) film derived from the wings of the glasswing butterfly to enhance the light absorption efficiency of FPSCs. We designed and fabricated the GSMA film with multilayers specifically for FPSCs. The suitable materials and nanostructures to adjust the refractive index are theoretically optimized. The GSMA film effectively improved the optical properties of PSC substrates, reducing reflectance (∼5.01%) and enhancing light transmittance (∼6.17%) in indium tin oxide (ITO)/PEN. In addition, the GSMA film on PEN maintains more than 94.70% of its initial transmittance even after being exposed to various harsh environments for 500 h, and GSMA film demonstrates flexibility by maintaining its initial structure even after a bending test (bending radius of 1 mm). The FPSCs and RPSCs assisted by GSMA film show high short-circuit current density (FPSC: ∼25.28 mA/cm², up to 26.05  mA/cm², RPSC: ∼24.27 mA/cm²) and power conversion efficiency (FPSC: ∼22.72%, RPSC: ∼22.31%), significantly narrowing the efficiency gap between FPSC and RPSCs.