Observation of Grain Boundary Passivation and Charge Distribution in Perovskite Films Improved with Anti-solvent Treatment

Abstract

Owing to the polycrystalline nature of hybrid perovskite thin films, the trap states in grain boundaries (GBs) introduced by charged defects play an important role in determining the charge collection efficiency and have a significant impact on their optoelectronic properties. Herein, we show the direct imaging of the GB passivation of perovskite films through an anti-solvent treatment and the anomalous charge distribution across the films due to the passivation. The downward band bending at the GBs has been observed at nanometer scale using Kelvin probe force microscopy. This revealed that a hot chlorobenzene treatment decreases the band bending at GBs and allows more homogeneous electronic properties throughout the film after passivation. Conductive atomic force microscopy has been employed to show the charge transport mapping across the films. It was found that the passivation effect not only changes the surface potential at GBs but also enhances the overall charge collection efficiency of the film. Our work provides a solution to reduce the density of charge defects at GBs through hot anti-solvent treatment, which is demonstrated to be a promising strategy to decrease the recombination losses at GBs and, thereby, increase the electronic quality of the perovskite films as well as enhance the device performance.

Synergistic Crystallization Modulation and Defects passivation via Additive Engineering Stabilize Perovskite Films for Efficient Solar Cells

“…Conversely, the films with KHFDFmodified, the GBs had a higher potential compared to the GIs, which revealed that the additives of KHFDF have the ability to passivate GBs and improve the CPD of GB. [64,65] Meanwhile, from the histograms in Figure 5g,h, we can observe that the films incorporated with KHFDF exhibit a much higher surface potential and a smaller range of CPD distribution relative to the FAMA films, which not only confirmed the UPS conclusions, but also indicated improved charge transport, suppressed carrier recombination and more homogeneous electronic properties. Furthermore, K + ions are seen to be mainly at the top and bottom surface interfacial regions of the perovskite layer, which can interact with undercoordinated I − and inhibit I − migration.…”

Lanthanide 3D Supramolecular Framework Boosts Stable Perovskite Solar Cells with High UV Utilization

“…The uniform current distribution and the overall current signal enhancement of the films after Tb‐cpon modification indicate that the conductivity of the films is improved. [ 43 ] In particular, the films have a stronger current signal at the GBs, which may be attributed to the reduced resistance due to the increased contact area of the conducting tip with the film. Figure 4f shows real‐time photos of different perovskite films annealed at 100 °C.…”

Insight into Controlled Surface Passivation of PEDOT:PSS for Defect Density Modulation and Efficient Charge Transport for Perovskite Solar Cells

“…Different techniques or compounds have been used to passivate the defects in the surface as well as the bulk along with grain boundaries. TAS is used to understand the type of defects and changes in defect states due to the passivation effect. − To get a clear insight into the hole extraction process at the interface, TAS can be used to probe the perovskite/HTL interface, which allows probing of the excited-state dynamics on different time scales. It is proven that surface passivation is more effective than bulk passivation in improving the PSC performance.…”