1. DNV GL, “Energy Transition Outlook 2019 Executive summary”
Global electricity demand
2. Indirect and direct band gap
DIRECT BANDGAP:
2.These kinds of materials are best
for fabricating optical sources.
1.Conduction and valence band both
are at k=0 and have the same
momentum.
3.The recombination of
electrons and holes happens
directly.
4.Recombination is radiative.
ex., Silicon, Germanium, etc.
INDIRECT BANDGAP:
1.Conduction and valence band are at different k
values and have different momentum.
2. These kinds of materials are not used to
fabricate optical sources.
3. Electron first goes to a point with the
same momentum, and recombination
happens.
4. Recombination is non-radiative.
ex., Gallium arsenide, Indium phosphide, etc.
Direct and Indirect band gap diagram
5. The UV-Vis absorption spectrum of Cs4CuSb2Cl12 double layered perovskite NCs in Hexane
STEADY-STATEABSORPTION (UV-Vis):
The absorption spectra of CCSC with
the capping ligands were recorded
employing a high-performance Cary
5000 UV-Vis-NIR Spectrophotometer
(Agilent Technologies) in the range of
200 nm to 800 nm. A quartz cuvette
having a path length of 1cm was used to
record the absorbance. Toluene was used
as a solvent for baseline correction after
testing the solubility of CCSC in it.
The resulting NC solution showed a dark black color, indicating its strong absorption in the
visible spectral region.
Experimentally, the peak was observed at 526 nm.
6. 6
TAUC PLOTANALYSIS FOR
FINDING BAND GAP:
The Tauc method is based on the assumption that the
energy-dependent absorption coefficient α can be
expressed by the following equation:
where h is the Planck constant, ν is the photon’s
frequency, Eg is the band gap energy, and B is a
constant. The γ factor depends on the nature of the
electron transition and is equal to ½ for the direct and
2 for the indirect transition band gaps. The analysis
was done using the software Origin.
The intersection point of the two tangents drawn was measured at 1.94 eV.
Therefore, the direct band gap energy of 1.94 eV was determined by Tauc plot analysis for
CCSC.
Determination of Bandgap of CCSC NCs
