Zdrojový dokument:Scientific papers of the University of Pardubice. Series A, Faculty of Chemical Technology. 20/2014
ISSN:1211-5541
Abstrakt:
A quantum dot solar cell is an emerging field in solar cell research that uses
quantum dots as the photovoltaic material. Quantum dots have band gaps that are
tunable across a wide range of energy levels by changing the quantum dot size.
The embedment of different sized dots within absorbing layer encourages
harnessing of the maximum spectrum energy. Also other effects like very high
surface to volume ratio, Quantum Transport make them attractive for future
devices. For an attempt of AIS quantum dots (QDs), AIS nanoparticles with
tetragonally distorted phase were prepared by mechanically alloying the
synthesized bulk AIS powder at room temperature in a planetary ball mill under
Ar. Nanoparticles are formed with range -10 nm in size. These ball-milled
nanoparticles contain different shapes, and the Rietveld analysis of X-ray powder
diffraction data reveals their detailed structural features. High resolution
transmission electron microscope (HRTEM) images also detect the presence of the tetragonal phase in ball-milled samples. Peak Broadening (FWHM), which is the
main characteristics of decrease in size, is observed. XRD data reveals the
downscaling of crystallite from 103 nm to 7 nm, also tetragonally distorted
structure of the system was not disturbed by milling. The DSC study also reveals
the phase evolution and crystallization kinetics. Bulk samples show endo melting
peak at 134 °C and 220 °C. Cooling-crystallization complexity of the peak/peaks
signifies crystallization from melt was heterogeneous nucleation and
crystallization from multiple types of centers. Unlike this, milled samples show two
crystallization effects at approx. 135 °C and 380 °C. Optical properties were
investigated to find band edges, and suggest it around 1.3 eV which is
encouraging for photovoltaic applications.