Enhanced absorption in organic solar cells using core-shell iron-ZnO nanoparticles: optical and numerical simulations

This study utilizes the finite-difference time-domain (FDTD) method to reveal the superior potential of cuboid iron (Fe) nanoparticles (NPs) with a zinc oxide (ZnO) shell for absorption enhancement (AE) in the active layer of organic solar cells (OSCs). The dimensions and arrangement of core-shell Fe-ZnO cuboid NPs on a ZnO substrate were meticulously optimized to achieve the highest AE. Unlike other noble metals, Fe NPs maintain or improve their enhancement capabilities even as the core thickness decreases and the shell thickness increases. In the 300–700 nm wavelength range, where the P3HT:PCBM composite has an intrinsic absorption spectrum, the absorption of ZnO nanostructures devoid of a metal core is reduced to 0.9 times the intrinsic value. In contrast, the absorption of the Fe-ZnO NPs increased to 1.282 times, which is 1.13 times greater than that of the Au NPs in the same structure. Additionally, the optical \(J_{sc}\) achieved by the Fe NPs is 1.75 times greater than the intrinsic \(J_{sc}\), which is 1.26 times greater than that achieved by the Au NPs. The electric field density and absorption density profiles indicate that Fe NPs significantly enhance organic absorption through localized surface plasmon resonance (LSPR), particularly in the red spectrum (700 nm), where P3HT:PCBM has the lowest intrinsic absorption.