t
p
are the Fresnel coefficients for parallel
polarized light,
β
is the angle of incident light,
γ
is the angle of
refracted light.
After determining the optical properties in TMM, the
generation coefficient is calculated using the quantum yield
function. The quantum yield is a logic function that takes 1 if
the photon energy is greater than or equal to the material's
bandgap, and 0 otherwise.
There are mainly 3 types of recombination in
semiconductors [42]: Radiative, Shockley-Read-Hall (SRH)
and Auger. Since silicon is an indirect semiconductor, it
mainly has SRH and Auger recombination, Radiative
recombination is almost absent. ZnO and perovskite are direct
semiconductors, they have three types of recombination.
Therefore, separate recombination models were used for each
region in the modeling. For example, since the emitter region
is made of ZnO or Perovskite, all three recombinations have
been declared to exist, and since the base is made of silicon,
only SRH and Auger recombinations have been declared to
exist. SRH recombination due to defects is calculated using
formula 3 [43].
(
)
(
)
2
,
1
1
n p i eff
SRH
net
p
n
n
p
np
n
R
n
n
p
p
−
=
+
+
+
(3)
Here: n is the electron concentration, p is the hole
concentration, γ
n
,γ
p
are the coefficients, τ
n
,τ
p
are the electron
and the hole lifetime, n
1
,p
1
are the electron and the hole
concentration on the trap.
Auger recombination is calculated using formula 4 [44] and
is also called three particles recombination. Accordingly, as
the concentration of charge carriers increases, so does its
portion in the total recombination. An increase in the input
concentration causes an increase in the concentration of charge
carriers. Therefore, after the input concentration reaches a
certain critical value, Auger recombination begins to
dominate.
(
)(
)
2
,
A
net
n
p
i eff
R
C n C p np n
=
+
−
(4)
Here: C
n
,C
p
are Auger coefficients. n
i,eff
is the intrinsic
carrier concentration.
The electrostatic field formed around the charge carriers
and ionized impurities and the electric potential are calculated
using the Poisson equation in formula 5 [45].
(
)
D
A
q
p
n
N
N
= −
− −
+
(5)
Here:
ε
is the permittivity,
N
D
and
N
A
are the concentrations
of donor and acceptor,
q
is the charge.
The internal electric field created by the ions in the p-n
junction separates the electron-hole pairs and help to reach
them to the contacts. So, unlike the diode, the drift movement
of charge carriers plays the main role in the solar cell. The
Masetti formula is given in formula 6 [46] was used to
calculate the mobility of charge carriers. Because in the
Masetti model, the effect of electron-phonon scattering, input
concentration and temperature are also considered.
Consequently, this model is suitable for estimating the
mobility of charge carriers in nanoparticle-incorporated solar
cells.
min 2
min1
,0
,0
,0
,0
1
,0
,0
exp
1 ((
) / )
1 (
/ (
))
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