Abstract— This paper presents the impact of incident angle of sun lights on the conversion efficiency of nano-structured GaAs solar cells. The incident light angle plays an important role on the conversion efficiency of GaAs solar cells or panels. Over the day, the incident angle of the sunlight falling on the solar cell or panel varies from morning to afternoon and influences the light capturing of the cells or panels, hence affecting the conversion efficiency. The nano-grating structure with effective incident angle can trap more sunlight into the solar cells. In simulation, different nano-grating structures are considered, such as elliptical, triangular, trapezoidal and rectangular shaped with various grating heights from 100-nm to 400-nm. Finite difference time domain (FDTD) simulation tool is used to simulate the light reflection, transmission and absorption in GaAs solar cells. From the simulation results, it has confirmed that the variation of incident light angle affects the light reflection losses, transmission, and absorption for all types of nano-grating shapes. Hence, this simulation results predicted that the light reflection loss is always least for the aspect ratio 0 ~ 0.5 at 0˚ incident angle, whereas the incident angle has less impact on the nano-grating height above 300 nm. Index Terms— Conversion efficiency, FDTD simulation, incident light angle, nano-grating structure, reflection loss, solar cell. I. INTRODUCTION In recent years, nano-structured gratings have been identified as a useful candidate to achieve high conversion efficiency of solar or photovoltaics (PV) cells due to their capacity to decrease the light reflection losses from the surface of the solar cells or panels. This nano-structured gratings can be accommodated as an anti-reflective (AR) coating to reduce the light reflection from the surface of solar or PV cells. For a single nano-grating structure, if the period is less than the wavelength of an incident light, then it performs like a homogeneous medium with an effective refractive index. So, the nano-structured grating can offer a gradual change in refractive index which confirmed an excellent AR coating and light capturing properties compared to a flat type or planar thin film [1-5]. In the earth, the solar or PV energy is plentiful but only a small fraction of it is used to produce the electricity. Presently most electrical energy still originates from the fossil fuels. However, the existing resources are non-renewable, fast reducing, so another approach of energy is required. Renewable sources, such as sunlight, hydroelectric, tides, waves, wind, geothermal and biomass can be utilized to produce the electricity and supply to the grids. This solar or PV energy is a pollution free clean energy and it is environmentally friendly. It doesn’t release any pollution to the atmosphere that affect the environment. Hence, the solar or PV cell is a very important research topic for ongoing implementation and production of renewable energy. In the nineteenth century, the solar or PV cell was discovered, since the research engineers and scientists have been trying to enhance the conversion efficiency which is about 20.3% for silicon solar cells as reported [2]. In solar or PV cells, there are various types of losses that decreases the cell conversion efficiency. Among these losses, the light reflection loss is one of the most dominant issue and it reduces the conversion efficiency of the cells significantly in conjunction with the incident light angle as it changes on non-tracking PV arrays. The thin-film AR coating can use to reduce the light reflection losses of solar or PV cells. For this instance, it can reduce the light reflection losses only for certain wavelengths but the process of AR coating is a very compound practice. However, this practice has several disadvantages, e.g., layer-to- layer adhesion, thermal mismatch between the materials and the volatility under thermal cycling [3, 4]. Hence, the nano- structured grating has several benefits over the AR coating as the refractive index changes slowly and leads to a lower reflection losses over the wide range of wavelengths and the light incidence angles [6-13]. In this paper, the impact of incident light angle on the nano- structured grating was investigated. In this simulation, different nano-gratings were used such as, elliptical, triangular (conical or perfect cone), trapezoidal (hatch top or truncated cone) and rectangular with various grating height ranging from 100 nm to 400 nm and different incident angles. The aim of this research is to reduce the light reflection losses and increase the quality light injection into the substrate. Finite difference time-domain (FDTD) simulation tool is used to simulate the nano-grating structures. The light reflection loss for a flat type substrate with zero incident angle (i.e., perpendicular to the surface) is more than 30%. For triangular-shaped nano-structured grating, the refractive index changes slowly and it behaves like a multi- layer AR coating. Hence, the light reflection loss reduces to ~5%. This simulation results confirmed that the light reflection loss rises with the increase of incident angles but for a typical nano-structure, the minimum light reflection loss is kept with the incident angle variation from -5° to +5°. Therefore, with optimum nano-structured gratings height and incident angles, the designed structure will reduce the light reflection losses and increase the conversion efficiency of GaAs solar cells. Manish Sharma, Narottam Das, Andreas Helwig, and Tony Ahfock School of Mechanical and Electrical Engineering, Faculty of Health, Engineering and Sciences, University of Southern Queensland, Toowoomba, QLD 4350, Australia E-mails: manishbsharma2002@gmail.com, narottam@ieee.org, Andreas.Helwig@usq.edu.au, and Tony.Ahfock@usq.edu.au Impact of Incident Light Angle on the Conversion Efficiency of Nano-structured GaAs Solar Cells Authorized licensed use limited to: University of Southern Queensland. Downloaded on April 20,2023 at 00:20:37 UTC from IEEE Xplore. Restrictions apply.