A New Strategy for Omnidirectional Broadband Absorption of the Solar Radiation for Thin-Film Solar Cells

Abstract

Thin films (TFs) are promising candidates for efficient low-cost solar cells (SCs). However, the reduced thickness poses a challenge for efficient optical absorption. This work demonstrates omnidirectional broadband absorption of polysilicon (p-Si) TFs decorated with light cone (LC) arrays composed of inverted cones decorated with sidewall subwavelength structures and top dielectric nanolenses. The study compares the optical absorption of p-Si samples: TF, TF with anti-reflection coating, TF decorated with optimized array of nanopillars (NP) each with SiO₂ nanolens, and TF decorated with a LC array. The height of the p-Si is 1.2 µm on top of a glass substrate. Specular, diffused and specular-diffused farfield spectroscopy are employed. The specular-diffused spectroscopy indicates that the broadband transmission and reflection of the LC array is 19.3% and 56.3%, respectively, lower than that of the NP array. Three-dimensional numerical calculations suggest that LC array provides an efficient mechanism for refracting the incoming photons into the array lateral directions combined with enhanced coupling of the incoming photons to the p-Si dielectrics. The performance of SCs based on LC arrays is numerically evaluated with a significant efficiency enhancement. The LC array paradigm paves the way for low-cost and efficient TF SCs.