The development of clean and renewable energy is needed urgently with the depletion of traditional energy sources [[1], [2], [3]]. Perovskite solar cells (PSCs) represent a promising thin-film technology [4,5] due to their high light absorption coefficient, extended carrier diffusion length, and cost-effective manufacturing within photovoltaic devices, which has attracted increasing attention.

However, inevitable optical loss in PSCs has become a significant challenge in achieving higher power conversion efficiency (PCE). The effective methods to improve PCE include up and down conversion layers [6,7], light trapping [8], plasmonic arrays [9,10], antireflection layers [11], and so on. Due to the refractive-index difference between air and substrate, there is reflection loss at the interface between air and substrate [12]. Antireflection layers are widely used to reduce surface reflection in optical devices, leveraging the interference of reflected light at the air-coating and coating-substrate interface [13].

Among antireflection layers, numerous research has been performed to study the characteristics of core-shell nanoparticles (NPs) [14,15]. Dielectric nanospheres are considered ideal materials for broadband antireflection [16], SiO2 NPs have been widely studied due to their advantages of no optical loss, non-toxicity, high stability, and low-cost advantages. Wang prepared a mesoporous SiO2 antireflection layer on PSCs using screen-printing technology and found that the short-circuit current density (Jsc) and PCE increased by about 3% [17]. Valiei simulated the SIO2/SiON antireflection layer on silicon solar cells by FDTD and PC1D methods. It was found that the PCE of the double-layer anti-reflective layer was about 7% higher than that of the single-layer antireflection layer [18]. However, the gradient effective refractive index gradient constructed by the SiO2 nanosphere array is still relatively large. Wu proposed SiO2@TiO2 NPs design and application on glass, improving the transmittance of glass [19]. Effects in core-shell thickness can have a great impact on the effective refractive index gradient, however, few studies have been conducted on SiO2@TiO2 NPs on PSCs and the effect of shell-thickness ratios (STRs) changes on their broadband absorption performance.

In this study, a nanostructure with an array of SiO2@TiO2 NPs on the surface of PSCs is proposed. The antireflection properties of PSCs are studied in detail by COMSOL Multiphysics, and the effects of STRs on PSCs are analyzed. The effects of different STRs on PSCs are explained by Fresnel equation and electric field intensity per volume (EFIPV). The results indicate that the antireflection layers with SiO2@TiO2 NPs exhibit superior performance in minimizing light reflection and enhancing electric field mode resonance in the visible spectra.

This article is structured as follows: the theoretical foundations and models will be described in section 2, the simulation results will be discussed in detail in section 3, and concluded in Section 4.