Cross-Sectional Investigations on Epitaxial Silicon Solar Cells by Kelvin and Conducting Probe Atomic Force Microscopy: Effect of Illumination

Abstract

Both surface photovoltage and photocurrent enable to assess the effect of visible light illumination on the electrical behavior of a solar cell. We report on photovoltage and photocurrent measurements with nanometer scale resolution performed on the cross section of an epitaxial crystalline silicon solar cell, using respectively Kelvin probe force microscopy and conducting probe atomic force microscopy. Even though two different setups are used, the scans were performed on locations within 100-μm distance in order to compare data from the same area and provide a consistent interpretation. In both measurements, modifications under illumination are observed in accordance with the theory of PIN junctions. Moreover, an unintentional doping during the deposition of the epitaxial silicon intrinsic layer in the solar cell is suggested from the comparison between photovoltage and photocurrent measurements.

A low Schottky barrier height and transport mechanism in gold–graphene–silicon (001) heterojunctions

“…So, it is possible to build point by point a map of local electrical resistance parallel to a topography map. 21 Results and discussion Fig. 1a shows the experimental spectrum of the C 1s core level for single layer graphene (G) on n-type Si(001):H. We introduced four components to obtain a reasonable t of the experimental curve.…”

High‐Throughput Electrical Potential Depth‐Profiling in Air

“…Knowledge of the depth profile of energetics at the interface is paramount to understanding the operation of thin film devices and two key methods for measuring this have matured. One involves a stepwise growth of a film onto a substrate with concurrent photoemission or Kelvin probe analysis performed in ultrahigh vacuum with interconnected deposition and analysis chambers and the other, is to cleave or mill and polish a complete device and measure the work function across the cross‐section using a scanning Kelvin probe force microscopy in air, or nitrogen atmosphere to minimize oxygen and humidity (if the measurement atmosphere was unstated in the paper it was presumed air). The stepwise approach using photoemission is more common and offers detailed electronic and chemical analysis with high surface sensitivity of ≈5–10 nm (laboratory based light source) but can be slow and cumbersome to perform, especially when the substrate is heated during the deposition and subsequently cooled to room‐temperature for analysis.…”

KPFM surface photovoltage measurement and numerical simulation

“…The tip work function didn't require calibration because only SPV measurement were performed and studied. Measurements were performed in the KPFM amplitude modulation (AM) mode rather than the frequency modulation (FM) one [1,2]. The AM mode was chosen because lateral resolution was not a problem on the homogeneous bulk samples studied, allowing focus on the superior surface potential resolution that can be achieved with the AM mode.…”

“…A bias applied via an external circuit is varied until the force and hence the electrostatic field between sample and KPFM tip is cancelled. There are a number of modes of operation as discussed in the original Rosenwaks paper [1] and subsequent work [2].…”