3 research outputs found
Contact lens field examiner
Low vision aids have not been successfully prescribed for many patients with peripheral visual field loss. In this experiment, visual field and visual acuity measurements for eighteen subjects with artificially restricted fields were made with and without two contact lens field expanders. The calculated visual efficiency was significantly improved with these devices which led the experimenters to believe that the potential of this device is very good for being a useful low vision aid
Nanoscale Surface Potential Variation Correlates with Local S/Se Ratio in Solution-Processed CZTSSe Solar Cells
Thin film solar cells made from Cu,
Zn, Sn, and S/Se can be processed
from solution to yield high-performing kesterite (CZTS or CZTSSe)
photovoltaics. We present a microstructural study of solution-deposited
CZTSSe films prepared by nanocrystal-based ink approaches using scanning
probe microscopy (SPM) and scanning electron microscopy (SEM) coupled
with energy dispersive X-ray spectroscopy (EDS). We correlate scanning
Kelvin probe microscopy (SKPM) maps of local surface potential with
SEM/EDS images of the exact same regions of the film, allowing us
to relate observed variations in surface potential to local variations
in stoichiometry. Specifically, we find a correlation between surface
potential and the S/(S + Se) composition ratio. In particular, we
find that regions with high S/(S + Se) ratios are often associated
with regions of more negative surface potential and thus higher work
function. The change in work function is larger than the expected
change in the valence band position with these small changes in sulfur,
and thus the data suggest an increase in acceptor-like defects with
increasing sulfur. These findings provide new experimental insight
into the microscopic relationships between composition, structure,
and electronic properties in these promising photovoltaic materials