RESEARCH ARTICLE Study of ultrathin-film amorphous silicon solar cell performance using photonic and plasmonic nanostructure Sigamani Saravanan | Raghvendra Sarvjeet Dubey Advanced Research Laboratory for Nanomaterials & Devices, Department of Nanotechnology, Swarnandhra College of Engineering & Technology, Narsapur, India Correspondence Sigamani Saravanan, Advanced Research Laboratory for Nanomaterials & Devices, Department of Nanotechnology, Swarnandhra College of Engineering & Technology, Narsapur - 534 280, West Godavari, Andhra Pradesh, India. Email: shasa86@gmail.com Summary The photonic and plasmonic nanostructures are highly feasible for enhanced light trapping mechanisms. These nanostructures hold great promises for bet- ter photovoltaic performance by yielding the highest light-harvesting photons within the few nanometer absorber regions. The shed light on the nano-scaled structures (thin films and nanogratings) is responsible for the highest scatter- ing mechanism with the omnidirectional diffraction angles and enhanced life time of the photons. In this research work, we have focused on improved ultrathin film amorphous silicon (a-Si) solar cell performance, which was inte- grated by top-SiO 2 and bottom-Ag nanogratings as a backside reflector by using rigorous coupled-wave analysis method. The SiO 2 antireflection coating, nanogratings, and absorber (a-Si) layer thicknesses were optimized for better photovoltaic performance. With the influence of optimization parameters, the highest current density of 27.03 and 33.53 mA/cm 2 were obtained from trans- verse electric and transverse magnetic polarization conditions due to the sur- face guided-mode, Fabry–Perot resonance, surface excitation, localized fields, and surface plasmon polariton modes. KEYWORDS Fabry–Perot, nanogratings, photonic, plasmonic, polarization 1 | INTRODUCTION Thin film is the promising technology for future energy needs; numerous ideas and design can lead the photovol- taic (PV) market. To tackle this problem, the scientific community has been attracted towards the nanophotonics and nanoplasmonic structures for the better optical perfor- mance by reduced cell thickness. Past two decades, PV technology has been developing with advanced and novel light trapping schemes. In solar cells, silicon-based thin film is the suitable choice as an absorber materials due to the low cost, naturally abundant, and compatible with existing fabrication technology for example crystalline sili- con (c-Si), amorphous silicon (a-Si), polycrystalline (p-Si), and micro-crystalline silicon (μc-Si). Past few decades, the combination of dielectric and metallic nanostructures showed significant optical performance in the solar cell device because of omnidirectional scattering, guided modes, and coupling the incident light into the absorber region such as nanoparticles, nanogratings, nanoshells, substrates, etc. 1-4 Particularly, the nanogratings can enhance the light absorption by the factor of 4n 2 (n-refractive index of the medium) by changing higher dif- fraction angles of incidence light and coupling the guided modes. 5 The performance of nanostructures has been changed by the reason of enhanced percentage of surface at minuscule. For that many approaches have been proposed in solar cells to improve the light absorption in the infrared spectral region. The finite element method (FEM), finite-difference frequency domain (FDFD), Received: 18 June 2021 Revised: 16 September 2021 Accepted: 18 September 2021 DOI: 10.1002/er.7328 2558 © 2021 John Wiley & Sons Ltd. Int J Energy Res. 2022;46:2558–2566. wileyonlinelibrary.com/journal/er