Subwavelength nanostructures evolving from hemispherical to spherical shapes for broadband anti-reflection in organic solar cells

We present subwavelength nanostructures with a periodic array that transitions from hemispherical to spherical shapes, achieving efficient broadband anti-reflection (AR) in organic solar cells (OSCs). Optimizing the shapes and geometrical parameters of an antireflective subwavelength nanostructure (ARSN) enhances absorption in the active layer across a broad wavelength range through reduced reflection. An OSC integrated with an optimized front-mounted ARSN, featuring a diameter of 100 nm, a spacing of 20 nm, and an aspect ratio of 0.9, achieves a short-circuit current density (JSC) of 27.89 mA/cm2, approximately 8.61 % higher than that of a conventional planar OSC. Additionally, we examine the AR properties of the ARSN by analyzing the optical admittance diagram, following the modeling of the ARSN using the effective medium approximation. This approach can be applied to other wavelength regions and a range of applications, including optoelectronic devices, displays, absorbers, and metasurfaces.