Analysis of Air Mass, EQE, and Spectroscopy: Physics Assignment

This physics assignment provides detailed solutions to several key concepts. The first section defines air mass and explains its measurement using a diagram, followed by an analysis of External Quantum Efficiency (EQE) and spectral response in solar cells. The assignment then delves into the concentration of energy, exciton diffusion, and open-circuit voltage in organic solar cells, calculating efficiency and energy changes. Finally, the assignment explores absorption spectroscopy, Raman spectroscopy, and photoluminescence measurements, explaining their principles and applications in material analysis. The document provides thorough explanations of each topic, including relevant equations and formulas.

Define the term air mass,
The air mass is the measure of how much atmosphere the sunlight will have to pass through
towards the surface of the earth.
With aid of a simple diagram show how air mass can be measured
The air mass do represents the section of atmosphere that the light will have to pass through
before it strike the Earth relative to its overhead path length, and is equal to Y/X.
Hence air mass can be determined by
AM = 1
cos (θ)
AM0 spectrum is the measure of spectrum at the point when there is no air between the sun and
the receiver.,
AM1 is the measure of spectrum when it travels through the atmosphere to the sea level when
the sun is directly overhead
AM 1.5 spectrum refers to two standard terrestrial solar spectral irradiance spectra, that include a
standard direct normal spectral irradiance and a standard total, within steradian field of view
of the tilted plane at from horizontal

Bi) External Quantum Efficiency (EQE)
This is the ratio between the number of photons that are emitted from the LED to the number of
electrons that are passing through the device in other words,
EQE = [Injection efficiency] x [Internal quantum efficiency] x [Extraction efficiency]
ii) spectral response is the ratio of the current generated by the solar cell to the power incident on
the solar cell.
iii) External Quantum Efficiency (EQE) of UV photodiodes.
With Photoresponsivity (R), in some papers, it is mentioned as,
EQE = 1240 x (R/λ)
while in some papers, it is mentioned it as,
EQE = 1240 x (R/λ) x 100%.
Where 'R' is Photoresponsivity and λ in the wavelength of incident light
c)
Jsc = q*∅∗EQC
Photon flux = h∗c∗I
l∗t
= 3∗1 08∗6.625∗1 0−34∗50
785∗109
Jsc= 3∗1 08∗6.625∗1 0−34∗50
785∗109∗1 019 ∗1.6∗1 019∗0.3
= 12.2 mA/cm2

Q2)
a) Is a mobile concentration of energy that are in the form of a crystals by an excited
electron and an associated hole on the surface of the organic solar cell
bi) concentration of photogenerated excitation at depth x
ii) exciton diffusion length
iii) exciton diffusion coefficient
( c)

When the operation of the cell is done at an open circuit , then current(I) will be
equivalent to zero, that is I = 0, therefore the voltage that will be across the output will be
known as an open circuit voltage.
d)
change in energy = 4.84 – 3.83 ev = 1.01 ev
e = 1.6 * 10-19
v = 6.309 * 1018 volts
%efficiency = (Jmax * Vmax)/Pin
= 12∗6.309∗1018
100∗1018 * 100
= 75.7%
Q3)
a)
from the initial equation the parameters I0, n, RS, and RSH will not be measured directly.

Open-circuit voltage
When the operation of the cell is done at an open circuit , then current(I) will be equivalent to
zero, that is I = 0, therefore the voltage that will be across the output will be known as an open
circuit voltage.
If we neglect the shunt resistance.
Then final term of the characteristic equation, the open-circuit voltage VOC is:
Short-circuit current
at short circuit V = 0, hence the current will be known as short circuit current
Therefore, for a high-quality solar cell the value of RS and I0 should be low , whereas RSH should
be high.
Hence the short circuit current ISC is:
b)
The equivalent circuit of a solar cell
I = IL − ID − ISH
where
 I = output current (amperes)
 IL = photogenerated current (amperes)
 ID = diode current (amperes)

 ISH = shunt current (amperes).
Q4)
a) Absorption spectroscopy
This is a method of molecular spectroscopy which majorly uses characteristics of
wavelength that are dependent on absorption of materials in order to easily help in
identification and quantification of specific substances.
It is always known that several molecules will absorb either ultraviolet or visible light.
When the attenuation of beam is increased it will directly affect the absorbance of a
solution which will too increases. Therefore sample absorbs energy, that is photons, from
the radiating field, and the variation is the absorption spectrum.
b) Raman spectrposcopy
Vibrations which are resoundingly improved fall into a few general robotic classes. The
most well-known case is Franck-Condon improvement, in which a part of the ordinary
arrange of the vibration happens toward a path in which the atom extends amid an
electronic excitation. The more the particle extends along this pivot when it assimilates
light, the bigger the improvement factor. The effortlessly envisioned ring breathing (in-
plane extension) methods of porphyrins fall into this class.Vibrations which couple two
electronic energized states are additionally resoundingly upgraded, through a system
called vibronic improvement. In the two cases, improvement factors generally take after
the powers of the ingestion range. The more full hypothesis of reverberation
improvement is past the extent of this area.
Reverberation upgrade does not start at a pointedly characterized wavelength. Truth be
told, improvement of 5x to 10x is watched if the energizing laser is inside even a couple
of 100 wavenumbers beneath the electronic progress of a particle. This "pre-
reverberation" improvement can be tentatively helpful.

The Raman diffusing from a compound (or particle) adsorbed on or even inside a couple
of Angstroms of an organized metal surface can be 103 to 106 more prominent than in
arrangement. This surface-upgraded Raman diffusing is most grounded on silver,
however is detectable on gold and copper also. At pragmatic excitation wavelengths,
upgrade on different metals is immaterial. SERS emerges from two mechanisms:• The
first is an improved electromagnetic field delivered at the surface of the metal. At the
point when the wavelength of the episode light is near the plasma wavelength of the
metal, conduction electrons in the metal surface are energized into a broadened surface
electronic energized state called a surface plasmon reverberation. Particles adsorbed or in
closeness to the surface experience a particularly substantial electromagnetic field.
Vibrational modes typical to the surface are most emphatically enhanced.• The second
method of improvement is by the development of a charge-exchange complex between
the surface and analyte particle. The electronic advances of numerous charge move
edifices are in the obvious, so reverberation upgrade occurs. Molecules with solitary
match electrons or pi mists demonstrate the most grounded SERS. The impact was first
found with pyridine. Other sweet-smelling nitrogen or oxygen containing mixes, for
example, sweet-smelling amines or phenols, are emphatically SERS dynamic. The impact
can likewise been seen with other electron-rich functionalities, for example, carboxylic
acids.The power of the surface plasmon reverberation is reliant on numerous components
including the wavelength of the occurrence light and the morphology of the metal
surface. The wavelength should coordinate the plasma wavelength of the metal. This is
around 382 nm for a 5μm silver molecule, yet can be as high as 600nm for bigger
ellipsoidal silver particles. The plasma wavelength is to the red of 650nm for copper and
gold, the other two metals which indicate SERS at wavelengths in the 350-1000 nm
district. The best morphology for surface plasmon reverberation excitation is a little
(<100nm) molecule or a molecularly unpleasant surface.SERS is ordinarily utilized to
ponder monolayers of materials adsorbed on metals, including cathodes. Other prevalent
surfaces incorporate colloids, metal movies on dielectric substrates and, as of late,
varieties of metal particles bound to metal or dielectric colloids through short linkages.
Despite the fact that SERS permits simple perception of Raman spectra from arrangement
fixations in the micro molar (10x-6) range, non-reproducibility of quantitative
estimations has in the past defaced its utility for explanatory purposes. However,
standardization underway of SERS dynamic media is steadily improving its potential
around there too.
( c) photoluminescence measurements
Spectral photoluminescence (PL) is a non-contact, non-destructive, spectroscopy-based
measurement technique to probe the electronic structure of different materials. Spectral PL can
be used to obtain information on the emission properties of different heterostructures (quality
control) and/or crystal structure of the material.

Photoluminescence is a photon emission process that occurs during relaxation from electronic
and/or localized (defects) excited states. Charge carriers can recombine through Shockley-Read-
Hall (SRH) and radiative recombination simultaneously. The radiative recombination rate is
proportional with the product of electron and hole concentrations. As the minority carrier density
is decreased by the SRH recombination that takes place at defects and impurities, the radiative
recombination is inversely proportional to defect density and impurity concentration. During
radiative recombination, a photon is emitted, which can be detected by a spectrograph. This is
the photoluminescence (PL) signal.