scholarly journals Kelvin probe force microscopy of nanocrystalline TiO2 photoelectrodes

2013 ◽  
Vol 4 ◽  
pp. 418-428 ◽  
Author(s):  
Alex Henning ◽  
Gino Günzburger ◽  
Res Jöhr ◽  
Yossi Rosenwaks ◽  
Biljana Bozic-Weber ◽  
...  
Keyword(s):  
Work Function ◽  
Surface Potential ◽  
Dye Sensitized Solar Cells ◽  
Kelvin Probe Force Microscopy ◽  
Light Illumination ◽  
Kelvin Probe ◽  
Nanocrystalline Tio2 ◽  
Force Microscopy ◽  
Illumination System ◽  
Surface Dipole

Dye-sensitized solar cells (DSCs) provide a promising third-generation photovoltaic concept based on the spectral sensitization of a wide-bandgap metal oxide. Although the nanocrystalline TiO2 photoelectrode of a DSC consists of sintered nanoparticles, there are few studies on the nanoscale properties. We focus on the microscopic work function and surface photovoltage (SPV) determination of TiO2 photoelectrodes using Kelvin probe force microscopy in combination with a tunable illumination system. A comparison of the surface potentials for TiO2 photoelectrodes sensitized with two different dyes, i.e., the standard dye N719 and a copper(I) bis(imine) complex, reveals an inverse orientation of the surface dipole. A higher surface potential was determined for an N719 photoelectrode. The surface potential increase due to the surface dipole correlates with a higher DSC performance. Concluding from this, microscopic surface potential variations, attributed to the complex nanostructure of the photoelectrode, influence the DSC performance. For both bare and sensitized TiO2 photoelectrodes, the measurements reveal microscopic inhomogeneities of more than 100 mV in the work function and show recombination time differences at different locations. The bandgap of 3.2 eV, determined by SPV spectroscopy, remained constant throughout the TiO2 layer. The effect of the built-in potential on the DSC performance at the TiO2/SnO2:F interface, investigated on a nanometer scale by KPFM measurements under visible light illumination, has not been resolved so far.

scholarly journals Quantification of electron accumulation at grain boundaries in perovskite polycrystalline films by correlative infrared-spectroscopic nanoimaging and Kelvin probe force microscopy

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Ting-Xiao Qin ◽  
En-Ming You ◽  
Mao-Xin Zhang ◽  
Peng Zheng ◽  
Xiao-Feng Huang ◽  
...  
Keyword(s):  
Solar Cell ◽  
Grain Boundaries ◽  
Cell Performance ◽  
Kelvin Probe Force Microscopy ◽  
Light Illumination ◽  
Kelvin Probe ◽  
Solar Cell Performance ◽  
Force Microscopy ◽  
Infrared Spectroscopic

AbstractOrganic–inorganic halide perovskites are emerging materials for photovoltaic applications with certified power conversion efficiencies (PCEs) over 25%. Generally, the microstructures of the perovskite materials are critical to the performances of PCEs. However, the role of the nanometer-sized grain boundaries (GBs) that universally existing in polycrystalline perovskite films could be benign or detrimental to solar cell performance, still remains controversial. Thus, nanometer-resolved quantification of charge carrier distribution to elucidate the role of GBs is highly desirable. Here, we employ correlative infrared-spectroscopic nanoimaging by the scattering-type scanning near-field optical microscopy with 20 nm spatial resolution and Kelvin probe force microscopy to quantify the density of electrons accumulated at the GBs in perovskite polycrystalline thin films. It is found that the electron accumulations are enhanced at the GBs and the electron density is increased from 6 × 1019 cm−3 in the dark to 8 × 1019 cm−3 under 10 min illumination with 532 nm light. Our results reveal that the electron accumulations are enhanced at the GBs especially under light illumination, featuring downward band bending toward the GBs, which would assist in electron-hole separation and thus be benign to the solar cell performance.

scholarly journals Work function difference of naphthyl end-capped oligothiophene in different crystal alignments studied by Kelvin probe force microscopy

2020 ◽  
pp. 106060
Author(s):  
Mads Nibe Larsen ◽  
Mads Svanborg Peters ◽  
Rodrigo Lemos-Silva ◽  
Demetrio A. Da Silva Filho ◽  
Bjarke Jørgensen ◽  
...  
Keyword(s):  
Work Function ◽  
Kelvin Probe Force Microscopy ◽  
Kelvin Probe ◽  
Force Microscopy ◽  
Work Function Difference ◽  
Function Difference

scholarly journals Measurement of electrostatic tip–sample interactions by time-domain Kelvin probe force microscopy

2020 ◽  
Vol 11 ◽  
pp. 911-921
Author(s):  
Christian Ritz ◽  
Tino Wagner ◽  
Andreas Stemmer
Keyword(s):  
Frequency Shift ◽  
Surface Potential ◽  
Electrostatic Force ◽  
Kelvin Probe Force Microscopy ◽  
Kelvin Probe ◽  
Force Microscopy ◽  
Atomic Force ◽  
Alternative Approach ◽  
Dc Component ◽  
Lock In

Kelvin probe force microscopy is a scanning probe technique used to quantify the local electrostatic potential of a surface. In common implementations, the bias voltage between the tip and the sample is modulated. The resulting electrostatic force or force gradient is detected via lock-in techniques and canceled by adjusting the dc component of the tip–sample bias. This allows for an electrostatic characterization and simultaneously minimizes the electrostatic influence onto the topography measurement. However, a static contribution due to the bias modulation itself remains uncompensated, which can induce topographic height errors. Here, we demonstrate an alternative approach to find the surface potential without lock-in detection. Our method operates directly on the frequency-shift signal measured in frequency-modulated atomic force microscopy and continuously estimates the electrostatic influence due to the applied voltage modulation. This results in a continuous measurement of the local surface potential, the capacitance gradient, and the frequency shift induced by surface topography. In contrast to conventional techniques, the detection of the topography-induced frequency shift enables the compensation of all electrostatic influences, including the component arising from the bias modulation. This constitutes an important improvement over conventional techniques and paves the way for more reliable and accurate measurements of electrostatics and topography.

scholarly journals Surface potential imaging and characterizations of a GaN p-n junction with Kelvin probe force microscopy

AIP Advances ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 085010
Author(s):  
Tomonori Nakamura ◽  
Nobuyuki Ishida ◽  
Keisuke Sagisaka ◽  
Yasuo Koide
Keyword(s):  
Surface Potential ◽  
Kelvin Probe Force Microscopy ◽  
Kelvin Probe ◽  
Force Microscopy

Relation between work function and structural properties of triangular defects in 4H-SiC epitaxial layer: Kelvin probe force microscopic and spectroscopic analyses

Nanoscale ◽  
2020 ◽  
Vol 12 (15) ◽  
pp. 8216-8229
Author(s):  
Hong-Ki Kim ◽  
Soo In Kim ◽  
Seongjun Kim ◽  
Nam-Suk Lee ◽  
Hoon-Kyu Shin ◽  
...  
Keyword(s):  
Work Function ◽  
Structural Properties ◽  
Epitaxial Layer ◽  
Kelvin Probe Force Microscopy ◽  
Kelvin Probe ◽  
Force Microscopy ◽  
Spectroscopic Analyses ◽  
Work Function Difference ◽  
Function Difference

In the defective SiC epitaxial layer, the work function variation was observed by Kelvin probe force microscopy (KPFM), and the work function difference came from the variation of polytype and the disordered surface.

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