Improving the performance of perovskite solar cells by adding 1,8-diiodooctane in the CH3NH3PbI3 perovskite layer

Abstract

In this study, different ratios of 1,8-diiodooctane (DIO) were added in the CH3NH3PbI3 perovskite layer of perovskite solar cells (PSCs). The effects of different ratios of DIO on the surface morphology of the perovskite layer were observed using an optical microscope (OM) and scanning electron microscope (SEM), whereas the surface roughness, crystal structure, and surface element bonding of the perovskite layer were observed using an atomic force microscope (AFM), X-ray diffractometer (XRD), and X-ray photoelectron spectroscope (XPS), respectively. The absorption spectrum of the perovskite layer was investigated using an ultraviolet–visible (UV/VIS) spectrometer, and the band gap of the perovskite layer was calculated. Furthermore, the PSCs with various ratios of DIO in the perovskite layer were analyzed using current density–voltage (J–V), external quantum efficiency (EQE), and electrochemical impedance spectrum (EIS) measurements. The results showed that adding DIO to the perovskite layer can reduce the nucleation rate of the perovskite through coordination, thereby enhancing the crystallinity, uniformity, and coverage of the perovskite layer and reducing its surface roughness to yield PSC device performance that is superior to a device without DIO. The resulting power conversion efficiency (PCE) increased from 10.77% without DIO to 12.86% with 1% DIO, which was a 19.4% increase, thus verifying that adding 1% DIO to the perovskite layer facilitated increasing the device performance of the PSC.