Unravelling the effect of defect density, grain boundary and gradient doping in an efficient lead-free formamidinium perovskite solar cell

Here we detailed a computational investigation of novel structured formamidinium tin tri-iodide (HC(NH2)SnI3or FASnI3where FA=formamidinium) perovskite solar cell. The proposed perovskite solar cell is of the architecture of glass substrate: fluorine-doped tin oxide (FTO)-oxide layer (OL)/Titanium di-oxide – electron transport layer (ETL)/ (HC(NH2SnI3−FASnI3) –perovskite absorber/spiro-omeTad-hole transport layer (HTL)/gold (Au) contacts. A power conversion efficiency of 21.24% was achieved using uniform doping and 21.5% with gradient doping. The incorporation of 0.01 μm grain boundary layer considerably effected the device performance and efficiency was dropped to 19.8%. The absorber layer parameters including layer thickness and defect density (or trap density) were also varied to inspect their impact on device performance. Further the paper also provide insights on the Mott-Schottky behavior, frequency dependent capacitance spectrum, optical absorption spectra, temperature variation impacts and the influence of resistance variation on device performance. The results of the quantum efficiency as a function of incident light wavelength depict that the proposed perovskite solar cell has a great potential to absorb a wider range of wavelengths (300 nm–900 nm) across the solar spectrum. The in-detail investigation of device characteristics revealed that the simulation model can become a useful guide in future fabrication of the efficient nano-structured formamidinium tin iodide based perovskite solar cells.