The Effect Of Solvent Treatment And Remnant PbI₂ On The Performance Of Perovskite Solar Cells

This work is focused on the investigation of the effect of solvent treatment and remnant PbI2 on the performance of provskite solar cells. The main contents of thesis include two parts.1.The dimethyl sulfoxide (DMSO) solvent pretreatment was introduced into the perovskite solar cell to improve its properties. The X-ray diffraction (XRD) has been used to analyze the remnant PbI2 in the film after the reaction and the morphologies of the perovskite and PbI2 films were investigated by using a scanning electron microscope (SEM). Current-Voltage (I-V), absorption and external quantum efficiency (EQE) measurements were carried out to investigate the differences in the properties between the devices with and without the solvent treatment. A significant improvement in short circuit current (Jsc) was found for the devices treated by DMSO. The efficiency achieved 11.1% for the treated devices, which inreased by 17.2% compared with the devices without solvent pretreatment. DMSO pretreatment can reduce the remnant of PbI2 and change the crystal size as well as surface morphology of perovskite film, which results in an enhanced performance.2.The optoelectric characteristics of the perovskite solar cells fabricated by one-step method and two-step method are investigated. The significant differences in main parameters of devices are found. The results show that the devices fabricated by one-step method have a larger short-circuit current and a higher fill factor. However, the devices fabricated by two-step method have a higher open-circuit voltage. For the sake of finding out the reasons that result in the different performances, the C-V and EQE measurements were carried out, and the open-circuit voltage dependence on the light intensity also be measured. Through the investigation, we found that remnant PbI2 formed a hole blocking layer between the PEDOT:PSS and the perovskite layer in peorskite solar cells fabricated by two-step method, which results in a enhanced open-circuit voltage and a lower photocurrent.