Use of Kelvin probe force microscopy to achieve a locally and time-resolved analysis of the photovoltage generated in dye-sensitized ZnO electrodes

Abstract

Kelvin probe force microscopy at air in the dark and under illumination by visible light was performed for electrodeposited porous ZnO films, which were sensitized by the indoline dye D149. A contact potential difference was measured that confirmed electron injection into the semiconductor matrix and their subsequent stabilization in trap states. A locally widely homogenous signal was observed speaking in favor of a wellcrystallized sample. The rise and decay times of the photovoltage in the ms to s timescale could be analyzed by use of individual scan lines or scanned images, respectively. The results are discussed in the context of recent pump-probe spectroscopy results as well as such from photoelectrochemical experiments with such electrodes and implications will be deduced for their use in dye-sensitized solar cells.

High-speed mapping of surface charge dynamics using sparse scanning Kelvin probe force microscopy

“…In timeresolved experiments, the sample often undergoes multiple global perturbations while the probe measures the local response at a specific nanoscale location before moving on to the next location. To date, tr-EFM and tr-KPFM have been applied to a variety of systems, including optoelectronic materials [16][17][18] , semiconductors for transistors [19][20][21] or memristors 22 , with temporal resolution ranging from 10 s to 1 ps [23][24][25][26][27] . While these approaches provide a detailed record of how the sample's properties evolve at each location over time, they are typically limited to fast processes that are fully reversible within the measurement window.…”

High speed mapping of surface charge dynamics via Spiral Scanning Kelvin Probe Force Microscopy

“…Speci cally, tr-EFM or tr-KPFM involve placing or slowly scanning a tip above a speci c location of interest while rapidly perturbing the sample at regular time intervals using an external stimulus (e.g., bias or light). So far, tr-EFM and tr-KPFM have been applied to a variety of systems, including photo-responsive materials [14][15][16] , semiconductors for transistors [17][18][19] or memristors 20 , with temporal resolution ranging from 10s to 1ps [21][22][23][24][25] . While these approaches provide a detailed record of how the sample's properties evolve at each location over time, they are slow and limited to processes that are cyclo-stationary, reversible, or at least reproducible within a short interval window.…”