KPFM and its Use to Characterize the CPD in Different Materials

Room-Temperature and Aqueous Solution-Processed Two-Dimensional TiS2 as an Electron Transport Layer for Highly Efficient and Stable Planar n–i–p Perovskite Solar Cells

“…In the following, the work function (WF) of ITO with the 2D TiS 2 film was determined by a Kelvin probe force microscope (KPFM) using highly oriented pyrolytic graphite (HOPG) as a reference and the measurement method referred in the literature. 42 As shown in Figure 2, the WF of pristine ITO was 4.75 eV, which is consistent with that reported in the literature. 43 Upon modification with 2D TiS 2 , the WF increased to 4.79 eV.…”

Inhibiting Interfacial Diffusion in Heterojunction Perovskite Solar Cells by Replacing Low‐Dimensional Perovskite with Uniformly Anchored Quaternized Polystyrene

“…In addition, the results of the KPFM test (Figure 3b, e) mentioned in the previous section shows that the average value of the surface potential of the perovskite film increased from 0.47 to 0.71 V. In the KPFM test, the potential of the film surface and the work function of the sample have the following relationship: $$\[ \begin{array}{*{20}{c}}{{V_{{\rm{cpd}}}} = \frac{{{\phi _{{\rm{tip}}}} - {\phi _{{\rm{sample}}}}}}{{ - e}}}\end{array} \]$$where V cpd refers to the potential of the film surface, ϕ tip is the work function of the tip, and ϕ sample represents the work function of the sample, and e is the elementary charge. [ 52 ] Therefore, this result also manifests the enhancement of the surface work function of the film, which is consistent with the UPS results.…”

“…where V cpd refers to the potential of the film surface, φ tip is the work function of the tip, and φ sample represents the work function of the sample, and e is the elementary charge. [52] Therefore, this result also manifests the enhancement of the surface work function of the film, which is consistent with the UPS results. Due to the presence of quaternary ammonium salt groups and conjugated benzene rings on the polymer, it is speculated that the increase in the work function and the valence band is probably due to the formation of interface dipoles which led to an increase in the vacuum energy level and an upward bending of the valence band.…”

In Situ Observation of Photoinduced Halide Segregation in Mixed Halide Perovskite

“…Atomic force microscopy (AFM) is an alternative to probing the photoreaction at the surface. In particular, Kelvin probe force microscopy (KPFM), one of the AFM extensions, can measure surface potential distribution recorded as contact potential difference (CPD). , Yun et al revealed that the grain boundaries act as a pathway for the migration of both photogenerated carriers and ions by monitoring the Coulombic interaction between the KPFM tip and the surface charges of the perovskite solar cell . Ma et al conducted the KPFM and conductive AFM for local observation of both surface Fermi level and photocurrent in MAPbI 3 as a function of temperature to investigate the effect of temperature-induced phase transition on the electrical properties of MAPbI 3 .…”