Cuprous iodide dose dependent passivation of MAPbI₃ perovskite solar cells

MAPbI₃ has been considered as a candidate for the active layer of perovskite solar cells in recent years. We proposed a device model to investigate the contribution of cuprous iodide (CuI) to MAPbI₃ perovskite thin films to power conversion efficiency (PCE) and demonstrated that the dosage of CuI affects the grain size of thin films and the PCE. Through the results of the SEM analysis, we found that the grain boundaries of MAPbI₃ perovskite films decreased with increases in the dosage of CuI and the grain size increased significantly from 164 nm ± 49 nm–299 nm ± 127 nm. In addition, the results of the PL measurement showed that the PL intensity decreased after addition of CuI to the MAPbI₃ perovskite thin films, suggesting a reduction in the charge recombination. The XRD patterns indicated that the addition of CuI did not influence the main structure of the MAPbI₃ perovskite. Interestingly, CuI plays a key role in the passivation of defects in MAPbI₃ perovskite thin films, which can reduce non-radiative recombination and increase the fill factor and open-circuit voltage of the device. In this study, we adjusted the grain size and passivated the MAPbI₃ thin film by controlling the dosage of CuI. We also increased the power conversion efficiency from 10% to 13%. This type of perovskite solar cell provided a simple, low cost preparation process for practical applications.