Optics Communications 454 (2020) 124437 Contents lists available at ScienceDirect Optics Communications journal homepage: www.elsevier.com/locate/optcom Efficiency improvement of a silicon-based thin-film solar cell using plasmonic silver nanoparticles and an antireflective layer Afsaneh Asgariyan Tabrizi a,∗ , Ali Pahlavan b a Department of Engineering, Sari Branch, Islamic Azad University, Sari, Iran b Department of Physics, Sari Branch, Islamic Azad University, Sari, Iran ARTICLE INFO Keywords: Silicon Thin films Solar cells Silver nanoparticles Absorption Efficiency Fill-factor Plasmonics ABSTRACT This paper presents a silicon thin-film solar cell (TFSC) integrated with the silver nanoparticles. It consists of anti-reflection, absorption and reflective layers in which the anti-reflective layer is made of pyramids of TiO 2 . The purpose of this structure is to allow sunlight to enter the cell at any angle with the minimum reflection and absorption in the wavelength range of 300–1100 nm. The absorbing layer is composed of silicon and when sunlight enters this layer, the molecular bonds break down and release many electrons due to its high absorption coefficient. In this layer, silver spherical nanoparticles are placed to increase the absorption of solar energy by the localized surface plasmon resonances, which will increase the efficiency of the TFSC. The last layer of the structure is a reflective surface of aluminum, which aims to reflect the light into the upper layer to enhance its absorption. We will calculate the key performance metrics for a solar cell such as short-circuit current, open-circuit voltage, fill-factor, and photovoltaic efficiency considering the effects of recombination between silicon substrate and other materials. The numerical results based on the finite-difference time-domain method reveal that the proposed structure has much more absorption due to the anti-reflection layer and the presence of silver nanoparticles that leads to light scattering, light localization, and guided mode excitation compared to conventional TFSC. Our simulations based on the finite-element method show the presented TFSC integrated with silver nanoparticles has a fill-factor of 0.82 and an efficiency of 16.18%. 1. Introduction A solar cell is a photovoltaic component that converts solar energy into an electric current. This is done using semiconducting materials with photovoltaic properties [1]. The research groups have focused on the principles and concepts of new photovoltaics including thin- film [2], organic [3], plasmonic [4–7], dye-sensitized [8–11], and photonic crystal [12,13] solar cells with the goal of reducing manu- facturing costs and used materials (consumables), as well as increasing the efficiency of solar cells. When incorporating nanophotonic elements similar to metallic nanoparticles with plasmon resonances tuned to efficiently scatter the light into the absorbing layer, or nanotextured surface anti-reflection coatings to decrease undesirable back reflections that degrade cell performance, solar cell efficiency can be dramatically enhanced [7,14,15]. In recent years, thin-film silicon solar cells have attracted much attention due to their low manufacturing costs, but their efficiency is relatively low compared to other structures [16]. The main problem is very low absorption at the edge of the con- duction band. Therefore, advanced schemes have been proposed to improve absorption based on light trapping in the active layer of a solar cell. In general, light-trapping methods are divided into (1): ∗ Corresponding author. E-mail addresses: asgariyan@gmail.com (A.A. Tabrizi), pahlavan@iausari.ac.ir (A. Pahlavan). reduce the reflection coefficient of the upper surface, and (2): increase the optical length inside the cell [17]. Various techniques have been presented by research groups to trap the sunlight including the use of anti-reflection coatings, rough surfaces [18,19], window grids [20], photonic crystals [21,22] and plasmon-based metallic nanoparticles [5, 23,24]. Among the above-mentioned methods, many studies are based on plasmonic nanoparticles. Indeed, plasmonic approach is one of the most desirable methods for improving localized light absorption [25, 26]. The study of metal nanoparticles in the upper layer of the solar cells shows a significant increase in the absorption of light [7]. It is caused by the scattering effect due to the excitation of surface plasmons. Increasing the absorption leads to lower recombination rate, higher open circuit voltage, higher conversion efficiency, and even new solar-cell designs. Since plasmonic metal nanostructures were used in the thin film solar cells, this led to strong light trapping due to the strong interaction of light in plasmonic nanostructures and surrounding media. Various structures have been proposed to increase the length of the optical pathway within the cell. Using structures with a periodic lattice is a simple way to increase the effective optical length because it can be contracted at both cell surfaces and increase the absorption https://doi.org/10.1016/j.optcom.2019.124437 Received 5 July 2019; Received in revised form 13 August 2019; Accepted 19 August 2019 Available online 22 August 2019 0030-4018/© 2019 Published by Elsevier B.V.