Enhancement of The Pb/Sn Perovskite Solar Cells Efficiency Using a Graded Bandgap Model in Absorber Layer

Abstract

Abstract In this paper, a SnO2:F/PCBM/MAPb1 − ySnyI3/PEDOT:PSS/Au perovskite solar cell with compositionally graded bandgap was designed to improve the power conversion efficiency (PCE). Notably, the bandgap energy (Eg) trend of MAPb1 − ySnyI3 compounds with several composition values, y, was utilized to select the grading profile. Applying typical values for the device parameters, simulations were performed with SCAPS. Higher bandgap materials were employed near the front and bottom interfaces of the absorber to control the recombination rate; however, lower bandgap materials were used in the middle of the absorber to improve the generation rate. The best model was achieved using y = 0.5 and y = 1 as two end materials. This model improved the PCE of the simulated Pb- and Sn-based solar cells by around 22.7% and 31.4%, respectively. The best PCE of 28.86% was obtained by dividing the absorber layer into three uniform parts of 1.18 eV (y = 0.5) and 1.3 eV (y = 1) and, optimizing their thicknesses. The proposed model increased the short-circuit current density (Jsc) to more than 37.7 mA/cm2, with an open-circuit voltage (Voc) of around 1.1 V. Finally, applying the parabolic grading for the bandgap shift between 1.18 eV and 1.3 eV showed that increasing the inner part thickness of the absorber, up to the value of 570 nm, will slightly enhance the PCE of the solar cell.