The Effect of Multi-walled Carbon Nanotubes and Reduced Graphene Oxide Doping on the Optical and Photovoltaic Performance of Ag2BiI5-Based Solar Cells

Abstract

Due to the nontoxic and air-stable nature of bismuth-based photovoltaic materials, they are suitable materials to replace lead-based perovskite ones. In this research, the influence of doping with multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO) on the structural, morphological, and optical properties of silver bismuth iodide (SBI) compounds was investigated. Structural characterizations revealed the formation of the hexagonal structure in SBI thin films, and also showed improvement in the surface morphology in the MWCNT and RGO-doped thin films. All absorber layers had a relatively high absorption coefficient above 104 cm−1 in the visible range, and the bandgap values varied between ∼ 1.83 eV and 2.04 eV. Also, we fabricated SBI-based solar cells, and their photovoltaic performance was studied. For the solar cell employing pure silver bismuth iodide, a photo conversion efficiency (PCE) of 0.44% was achieved. The inclusion of MWCNTs and RGO dopants in the SBI thin film PCE increased the device performance, and the highest PCE of 1.61% and 1.32% was obtained, respectively. The stability of the solar cells was also investigated under the environmental conditions. Results show that after 30 days, devices preserved about 90% of their efficiency.