Research ArticleTheoretical Study of Proton Radiation Influence on thePerformance of a Polycrystalline Silicon Solar Cell

Tchouadep Guy Serge, Zouma Bernard , Korgo Bruno, Soro Boubacar,Savadogo Mahamadi , Zoungrana Martial , and Zerbo Issa

Laboratoire d’Energies Thermiques REnouvelables (LETRE), UFR-SEA, Département de Physique,Université Joseph KI-ZERBO de Ouagadougou, Burkina Faso

Correspondence should be addressed to Zoungrana Martial; zoungranamartial@gmail.com

Received 23 August 2019; Revised 31 October 2019; Accepted 5 December 2019; Published 29 December 2019

Academic Editor: Alberto Álvarez-Gallegos

Copyright © 2019 Tchouadep Guy Serge et al. This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

The aim of this work is to study the behaviour of a silicon solar cell under the irradiation of different fluences of high-energy protonradiation (10MeV) and under constant multispectral illumination. Many theoretical et experimental studies of the effect ofirradiation (proton, gamma, electron, etc.) on solar cells have been carried out. These studies point out the effect of irradiationon the behaviour of the solar cell electrical parameters but do not explain the causes of these effects. In our study, we explainfundamentally the causes of the effects of the irradiation on the solar cells. Taking into account the empirical formula ofdiffusion length under the effect of high-energy particle irradiation, we established new expressions of continuity equation,photocurrent density, photovoltage, and dynamic junction velocity. Based on these equations, we studied the behaviour of someelectronic and electrical parameters under proton radiation. Theoretical results showed that the defects created by theirradiation change the carrier distribution and the carrier dynamic in the bulk of the base and then influence the solar cellelectrical parameters (short-circuit current, open-circuit voltage, conversion efficiency). It appears also in this study that, at lowfluence, junction dynamic velocity decreases due to the presence of tunnel defects. Obtained results could lead to improve thequality of the junction of a silicon solar cell.

1. Introduction

In order to improve the efficiency of solar cells embedded inspace, mainly by satellites, deep studies about silicon solarcells in radiation environment have been carried with themain focus to build theoretical models for silicon space solarcell damage [1], leading experimental study to understanddamage effect induced by gamma rays [2]. The study ofsemiconductor device behaviour under high-energy particlesis extremely important. Several work articles have investi-gated the theoretical external factors dependence of solar celloutput parameters and the analysis provided importantinformation. The study of the influence of 1MeV electronirradiation on electrical parameters of solar cell showed thatradiation-induced defects are considered as recombination

centers and lead to degradation of the open-circuit photo-voltage Voc, the short-circuit photocurrent density Jsc, andthe maximum power Pm [3–5]. The study of the impact ofirradiation on shunt resistance showed that it is reducedwith increasing of particle fluences [6]. It has been shownthat radiation induced damage which manifests itself inimportant ways [7]: increase in leakage current, caused bythe formation of mid-gap generation and recombinationcenters; generation of recombination centers proportionallyto the increase of particle fluence; change of effective dopingconcentration of the cell; and reduction of charge collectionefficiency due to charge carrier trapping in defect stateswithin the bandgap. Some studies [8, 9] also show that atthe first order, the degradation rate of the short-circuit cur-rent (Isc) of a solar cell is the function of the absorption

HindawiInternational Journal of PhotoenergyVolume 2019, Article ID 8306492, 7 pageshttps://doi.org/10.1155/2019/8306492

coefficient of its composing material, while the degradationrate of the open-circuit voltage (Voc) depends on the regimeof study, carrier’s diffusion or recombination. These twophenomena lead to the degradation of the solar cell maxi-mum power.

In these studies, the authors point out the effect irradia-tion on the behaviour (increase, decrease) of the solar cellelectrical parameters but do not explain the causes of theseeffects. In this paper, we present a fundamental study thatexplains the causes of the effects of the irradiation on thesolar cells. Firstly, we explain fundamentally the causes ofthe effects of the defects created by the irradiation on the car-rier distribution in the bulk of the base. Secondly, we makethe connection between the carrier distribution and thedefects created by the irradiation of the solar cell to explainfundamentally the behaviour of the dynamic of the chargecarriers at the junction of the solar cell, and then, on its elec-trical parameters.

2. Materials and Methods

2.1. Analytical Formulation. This study considers a solarcell irradiated with a low fluence (less than 1013 cm-2) of10MeV protons under multispectral illumination. In thisrange of energy, distribution of defects is uniform [10],so we can consider a simplified model in which diffusionlength is sufficient to characterize the degradation of thesolar cells under high-energy particles [11, 12]. The studyhas been done in the theory of quasineutral basis (QNB)hypothesis [13].

Under these conditions, the equation of charge carrierdistribution in the bulk of the base is given as follows:

∂2δ xð Þ∂x2

−δ xð ÞL∗n

2 = −G xð ÞDn

: ð1Þ

In this expression,GðxÞ =∑3

i=1ai ⋅ exp ð−bi ⋅ xÞ is the carrier generation rateat x position [14, 15], L∗n is the difusion length of the minoritycharge carriers,Dn is the minority carrier diffusion coefficientbefore irradiation, δðxÞ is the photogenerated minority car-rier density at the depth x in the base, ai and bi are the coef-ficients deduced from modelling of the generation rateconsidered for overall the solar radiation spectrum underAir Mass 1.5 standard conditions [14].

L∗n is given as follows:

1L∗n

2 =1L20

+ Kl ⋅Φ, ð2Þ

where L0 is the diffusion length before irradiation, Ф is thefluence, and Kl is the damage rate related to the materialfor a given energy of radiation (Kl = 5:6:10−7) [16].

By injecting Equation (2) into Equation (1), we obtaineda general continuity equation of minority charge carriers

which is a second-order differential equation with constantcoefficients.

The general solution of Equation (1) is given by [17–19]:

δ x,Φð Þ = A∗ cosh α∗ ⋅ xð Þ + B∗ sinh α∗ ⋅ xð Þ

+ 〠3

i=1

aiDn α∗2 − b2i

� � ⋅ exp −bi ⋅ xð Þ,ð3Þ

with α∗ = 1/L∗n and α∗2 − bi2 ≠ 0:

The following boundary conditions were used [17, 19]:

(i) At the junction (x = 0)

Dn ⋅∂δ x,Φð Þ

∂x

����x=0

= Sf ⋅ δ 0,Φð Þ ð4Þ

(ii) At the back surface (x =H)

Dn ⋅∂δ x,Φð Þ

∂x

����x=H

= −Sb ⋅ δ H,Φð Þ ð5Þ

The coefficients A∗ and B∗ can be determined by using theprevious boundary Conditions (4) and (5). In Equations (4)and (5), the expressions Sf and Sb are, respectively, thejunction dynamic velocity and the back surface recombina-tion velocity.

The junction dynamic velocity Sf characterizes carrierbehaviour at the solar cell junction trough two phenom-ena [20]:

(i) The carrier intrinsic losses at the solar cell junctioninterface, characterised by the carrier intrinsic junc-tion recombination velocity Sf0

(ii) The carrier diffusion through the solar cell junctionimposed by the external load and characterized bythe carrier diffusion velocity Sf j

The junction dynamic velocity Sf, which is a carrier col-lection rate at the junction, is the sum of these two compo-nents: Sf = Sf0 + Sf j.

2.2. Expression of Electronic and Electrical Parameters

2.2.1. Photocurrent Density. Photocurrent density expressionis given as follows [17–19]:

Jph Sf ,Φð Þ = qDn∂δ x, Sf ,Φð Þ

∂x

�x=0

: ð6Þ

The short-circuit current density is given by the rela-tionship:

2 International Journal of Photoenergy

2.2.2. Intrinsic Junction Recombination Velocity. The intrin-sic junction recombination velocity is obtained by solvingthe equation as follows [17, 19]:

∂Jph∂Sb

= 0 for Sb⟶∞: ð9Þ

The solution of Equation (9) gives:

2.2.3. Photovoltage. The Boltzmann law leads to an expres-sion of the photovoltage of the solar cell which depends onthe charge carrier concentration at the junction. Its expres-sion is as follows [17, 19]:

Vph Sfð Þ =VT ⋅ lnδ 0, Sfð Þ

n0+ 1

� �, ð11Þ

with n0 = ni2/NBand VT = kB:T/q:

n0 is the density of the electrons at thermodynamic equi-librium; ni is the intrinsic concentration of the electrons(ni = 1010cm−3); q is the elementary charge; NB is the dopingdensity of the base (NB = 1016cm−3); VT is the thermal volt-age (VT = 26mV) at T = 300K ; kB is the Boltzmann constant.

The open-circuit voltage is obtained for the dynamicjunction velocity equal to zero:

Voc =Vph Sf = 0ð Þ: ð13Þ

2.2.4. Conversion Efficiency. The solar cell conversion effi-ciency which is the relationship between the output powerand the incident light power is given by the followingequation:

η =Pel Sfmaxð Þ

Pinc, ð14Þ

where Pincis the incident light power ð1000W:m−2Þ.

3. Results and Discussion

3.1. Influence of Irradiation on Electronic Parameters

3.1.1. Influence of Irradiation on the Junction DynamicVelocity. The influence of the irradiation on the solar cellmanifests itself through its influence on the quality of thesolar cell material, and then, on the quantity of carriers thatescape from the recombination to produce a current. Thejunction dynamic velocity Sf ðSf = Sf 0 + Sf jÞ characterizesboth carrier intrinsic recombination at the junction (Sf 0)and the carrier diffusion through the junction (Sf j) [16, 21].For a given illumination, and a given external load (Sf j),the quantity of carriers that can be collected at the junctionof the solar cell (related to Sf ) will vary with the quality of

Jsc = limSf→∞

Jph ð7Þ

Jsc = qDn ⋅ 〠3

i=1

aiDn ⋅ α∗2 − bi

2� � ⋅α∗ ⋅ Sb −Dn ⋅ bið Þ ⋅ cosh α∗ ⋅Hð Þ − e−bi ⋅H

� �+ Dn ⋅ α∗

2 − Sb ⋅ bi� �

⋅ sinh α∗ ⋅Hð ÞSb ⋅ sinh α∗ ⋅Hð Þ +Dn ⋅ α∗ ⋅ cosh α∗ ⋅Hð Þ : ð8Þ

Sf 0 =Dn ⋅ α∗ ⋅

∑3i=1 ai/ Dn ⋅ α∗

2 − bi2

� �� �⋅ α∗ ⋅ sinh α∗ ⋅Hð Þ + bi ⋅ cosh α∗ ⋅Hð Þð Þ ⋅ e−bi ⋅H − bi� �� �

∑3i=1 ai/ Dn ⋅ α∗2 − bi

2� �� �⋅ α∗ ⋅ cosh α∗ ⋅Hð Þ + bi ⋅ sinh α∗ ⋅Hð Þ ⋅ e−bi ⋅H� �

− α∗� �� � : ð10Þ

Vph = VT ⋅ ln1n0

⋅ 〠3

i=1

aiDn ⋅ α∗2 − bi

2� � ⋅Dn ⋅ α∗ ⋅ Dn ⋅ bi − Sbð Þ ⋅ e−bi ⋅H − cosh α∗ ⋅Hð Þ� �

Dn ⋅ α∗ð Þ2 + Sf ⋅ Sb� �

⋅ sinh α∗ ⋅Hð Þ +Dn ⋅ α∗ ⋅ Sf + Sbð Þ ⋅ cosh α∗ ⋅Hð Þ +

Dn ⋅ Dn ⋅ α∗2 − Sb ⋅ bi

� �⋅ sinh α∗ ⋅Hð Þ

Dn ⋅ α∗ð Þ2 + Sf ⋅ Sb� �

⋅ sinh α∗ ⋅Hð Þ +Dn ⋅ α∗ ⋅ Sf + Sbð Þ ⋅ cosh α∗ ⋅Hð Þ

2666664

3777775

+1

8>>>>>>>><>>>>>>>>:

9>>>>>>>>=>>>>>>>>;

:

ð12Þ

3International Journal of Photoenergy

the material of the solar cell, and then, with the carrier intrin-sic recombination at the junction (related to Sf 0). We canthen deduce that the influence of the particle fluence on thejunction dynamic velocity results in its influence on theintrinsic recombination velocity Sf 0 of the solar cell.

The curve in Figure 1 shows the effect of the increaseof particle’s fluence on the solar cell junction dynamicvelocity Sf = Sf 0 + Sf j. In the expression of the junctiondynamic velocity (Sf ), Sf 0 is the intrinsic junction recom-bination velocity given in Equation (10), and we consideran intermediate operating value of carrier diffusion veloc-ity Sf j: Sf j = 104 cm:s−1:

It appears on this curve that with the increase of the flu-ence, the junction dynamic velocity has two behaviours.

For a low value of the fluence (Φ < 1010P:cm‐2), weobserve a decrease of the junction recombination velocity.When we increase the particle fluence, we increase also thedefects in the materials of the solar cell and at its junction.

With the increase of the defects at the junction of thesolar cell, the quantity of carriers that must be collected atthe junction will be reduced, and then will lead to a reductionof the carrier diffusion velocity (Sf j) and beyond a reductionof the junction dynamic velocity (Sf ). For a given operatingpoint, the increase of the fluence leads to a situation wherethe quantity of defects created at the junction of the solar cellrecombines all the carriers that must cross this junction. So,the carrier diffusion velocity is null (Sf j = 0). This situationcorresponds to the minimum of the curve and for this partic-ular value of the fluence of particles (Φ = 1010P:cm‐2), thejunction dynamic velocity (Sf ) equals to intrinsic recombina-tion velocity at the junction (Sf 0). Beyond this value of thefluence (Φ = 1010P:cm‐2), the quantity of defects created atthe junction is more than the quantity of carriers that mustcross the junction, and then, the excess of the defects leadsto an increase of the intrinsic recombination velocity (Sf 0).For these values of the fluence, the increase of the junctiondynamic velocity is only the consequence of the increase ofthe intrinsic recombination velocity due to the material ioni-sation by the fluence of particles.

3.1.2. Influence of Irradiation on Carrier Density Profile in theBase. The curves in Figure 2 show the effect of the particle’sfluence on the variation of carrier density along the basedepth of the solar cell in short-circuit situation.

We observe on these curves that the maxima of thecarrier density decreases with the increase of the fluence ofparticles. The decrease of the carrier density maxima charac-terizes a reduction of photogenerated carriers in eachposition x in the bulk of the base. This situation can beexplained by the fact that the increase of the fluence leadsto a generation of more defects which acts mainly as recom-bination centers [22].

Indeed, the increase of the fluence means an increase ofthe quantity of particles that reaches on the solar cell. Theseparticles create displacements and ionisation defects in thelattice of the material [23] and then lead to the increase ofcarrier recombination in the base. The decrease of carrierdensity with the increase of the fluence should result in the

decrease of the solar cell photocurrent and therefore to anincrease of its series resistance [24].

We also note that with the increase of the fluence, thepeaks of the curves move toward the junction of the solar cell.This phenomenon is interpreted as the consequence of theincrease of the defects with the increase of the fluence andthat leads to a reduction of the quantity of carriers whichcross the junction to participate to the photocurrent. Thisphenomenon is also the consequence of the fact that radia-tion increases the depth of the space charge region by pro-ducing diffusion of phosphorus atoms in the emitter [25].

The curves in Figure 3 show the effect of the increase ofparticle’s fluence on the charge carrier density for variouspositions in the base of the solar cell.

We observe on these curves that at various position in thebulk of the base, carrier density decreases with the increase ofthe particle’s fluence reaching on the solar cell. This phenom-enon is due to the increase of the defects which acts as recom-bination centers.

We also note that for the values of the particle’s fluenceless than 7.107 P.cm-2 (Φ < 7:107P:cm‐2) the carrier densitiesat the base depth near the junction (x < 0:004) are smallerthan those of the farthest depths of the base (x > 0:004).This situation can be explained by the fact that the effectof the small values of the fluence (Φ < 7:107P:cm‐2) on thecarrier density is not noticeable. So, all the carriers photo-generated near the junction cross this region to participateto the photocurrent, and this situation explains the smallvalues of the carrier densities in the region near the junction.For more remote positions of the junction (x > 0:004), thecarriers have the time to accumulate, and this situationexplains the high values of the carrier density at this positionof the junction.

We observe also that for the values of fluence higher than7.107 P.cm-2 (Φ > 7:107P:cm‐2), the carrier density decreasesas we go far in the depth of the base.

These results are also in agreement with the inversion ofthe curve of junction dynamic velocity observed in Figure 1while the fluence is equal to Φ = 7:107P:cm‐2, but also withthe decrease of carrier density in the base depth with theincrease of particle’s fluence observed on the curve inFigure 3.

Indeed, the high values of the carrier density observed forthe low fluence of the particles (Φ < 7:107P:cm‐2) at theregion near the junction (x < 0:004) are the consequence ofthe reduction of the carrier diffusion velocity (Sf j) with theincrease of the fluence observed in Figure 1. The decreaseof the carrier density in the deeper regions of the base is theconsequence of the increase of carrier recombination in thebase, due to the increase of defects in the lattice of the mate-rial with the increase of the fluence of the particles observedin Figure 3.

3.2. Influence of Irradiation on Electrical Parameters

3.2.1. Influence of Irradiation on Short-Circuit Current Density.The curve in Figure 4 shows the effect of the increase ofparticle’s fluence on the short-circuit current density of thesolar cell.

4 International Journal of Photoenergy

We observe on this curve that with the increase of the flu-ence of the particles on the solar cell, the short-circuit currentdensity decreases. The decrease of the short-circuit currentdensity results from the reduction of the quantity of carrierswhich cross the junction of the solar cell to participate to thephotocurrent, and then, is and accordance none the less withthe decrease of junction diffusion velocity [24] but also withthe decrease of carrier density when the fluence of the parti-cles on the solar cell increases.

3.2.2. Influence of Irradiation on Open-Circuit Voltage. Thecurve in Figure 5 shows the effect of the increase of particle’sfluence on the open-circuit voltage of the solar cell.

The photovoltage is directly linked to the carrier concen-tration in the bulk of the base. As the increase of the fluenceof the particles leads to an increase of the material defects by

Fluences (P.cm2)0.0 2.0 × 1011 4.0 × 1011 6.0 × 1011 8.0 × 1011 1.0 × 1012

1 × 1012

0

2 × 1012

4 × 1012

6 × 1012

7 × 1012

8 × 1012

9 × 1012

Carr

iers

den

sity

(cm

−3 )

x = 0.002 cmx = 0.004 cm

x = 0.006 cmx = 0.008 cm

Figure 3: Carrier density versus particle’s flux at various positionx in the base (L0 = 0:02 cm; Sb = 4:104 cm:s−1; Sf = 8:108 cm:s−1;Dn = 27 cm2:s−1; H = 0:03 cm; Kl = 5:6:10−7).

0.020

0.022

0.024

0.026

0.028

0.030

0.032

Fluences (P.cm2)

0.0 2.0 × 1011 4.0 × 1011 6.0 × 1011 8.0 × 1011 1.0 × 1012

Shor

t circ

uit c

urre

nt d

ensit

y J s

c (A

.cm2 )

Figure 4: Short-circuit current density versus fluence (L0 = 0:02 cm;Sb = 4:104 cm:s−1; Sf = 8:108 cm:s−1; Dn = 27 cm2:s−1; H = 0:03 cm;Kl = 5:6:10−7).

Inversionarea (disappearance)of tunnel-type defects and

appearance of complexdefects)

Fluences (P.cm−2)0.0 2.0 × 1011

6.0 ×1 03

8.0 × 103

1.0 × 104

1.2 × 104

1.4 × 104

1.6 × 104

1.8 × 104

2.0 × 104

2.2 × 104

4.0 × 1011 6.0 × 1011 8.0 ×1 011 1.0 ×1 012

Junc

tion

dyn

amic

velo

city

(cm

.s−1 )

Figure 1: Junction dynamic velocity versus fluence.

0.000 0.005 0.010 0.015 0.020 0.025 0.030Base depth (cm)

2.0 × 1012

0.0

4.0 × 1012

6.0 × 1012

8.0 × 1012

1.0 × 1013

Carr

iers

den

sity

(cm

−3

)

𝛷 = 0 (P.cm−2)𝛷 = 109 (P.cm−2)𝛷 = 1010 (P.cm−2)

𝛷 = 5.1010 (P.cm−2)𝛷 = 7.1010 (P.cm−2)𝛷 = 1011 (P.cm−2)

Figure 2: Carrier density versus base depth for different values ofthe fluence (L0 = 0:02 cm; Sb = 4:104 cm:s−1; Sf = 8:108 cm:s−1;Dn = 27 cm2:s−1; H = 0:03 cm; Kl = 5:6:10−7).

5International Journal of Photoenergy

ionisation, then to an increase of carrier recombination in thebase, it will result a reduction of carrier concentration in thebase. That explains the decrease of the open-circuit voltagewith the increase of the fluence of the particles on the solarcell. This is also in accordance with the decrease of carrier’sdensity and the increase of diffusion velocity with theincrease of the fluence of the particles on the solar cell.Indeed, these two situations lead to a reduction of carrierconcentration in the base.

3.2.3. Influence of Irradiation on the Efficiency. The curve inFigure 6 shows the effect of the increase of the fluence ofthe particles on the conversion efficiency of the solar cell.

It appears on this figure that the conversion efficiency ofthe solar cell decreases when the fluence of the particles onthe solar cell increases. This result is in accordance with thebehavior of the short-circuit current density and the open-circuit voltage under the effect of the intensification of theirradiation. Indeed, as the conversion efficiency is functionof the electric power, and then of the photocurrent and thephotovoltage, their decrease will lead to a decrease of the con-version efficiency.

We present in Table 1 the values of the short-circuit cur-rent density, the open-circuit voltage, the maximum electricpower, and the conversion efficiency of the solar cell for fivedifferent values of fluence.

We observe on the results of this table that all the electri-cal parameters (short-circuit current density, open-circuitvoltage, maximum electric power, and conversion efficiency)decrease with the increase of the intensity of the fluence ofthe particles on the solar cell. The irradiation affects thenstrongly the electrical parameters of the solar cell. For anincrease of the proton radiation fluence from 0 to1012 P.cm-2, the efficiency drops from 15.561% to 6.589%.

4. Conclusions

This work put in evidence the effect of the particle (protons)irradiation on the performance of a silicon solar cell. By solv-

ing the continuity equation with the assumption that protondamage results in a modification of the diffusion length, weobtained new expressions of the excess minority carrier den-sity, junction dynamic velocity, photocurrent density, andphotovoltage. It appears through the study of the radiationinfluence on these parameters that the carrier density andthe junction dynamic velocity decrease with the increase ofthe fluence of the particles in all levels of the base depth. Fun-damentally, this situation can be explained by the fact thatthe increase of the irradiation increases the ionisation of thesolar cell materials by the incident particles and then leadsto the increase of the defects in the bulk of the base and atthe solar cell junction. The increase of the defects increasesthe recombination of the carriers photogenerated in the baseand then leads none the less to the reduction of the carrierdensity in the base but also to the reduction of carrier diffu-sion through the junction. This study put in evidence also acritical value of the irradiation (Φ = 1010P:cm‐2) for whichthe junction dynamic velocity (Sf ) equals to intrinsic recom-bination velocity at the junction (Sf 0). For this value of thefluence, all the carriers that must cross the junction arerecombined intrinsically at the junction (Sj = 0). We observealso in this study that in accordance with the reduction ofcarrier density in the base of the solar cell with the increaseof the fluence, the short-circuit current density, the open-circuit voltage, the maximum electric power, and the conver-sion efficiency decrease also. These results show the stronginfluence of the irradiation on the performance of the siliconsolar cell.

Fluences (P.cm2)0.0 2.0 × 1011 4.0 × 1011 6.0 × 1011 8.0 × 1011 1.0 × 1012

Ope

n ci

rcui

t vol

tage

Voc

(V)

0.60

0.58

0.56

0.54

0.52

Figure 5: Open-circuit voltage versus fluence (L0 = 0:02 cm; Sb =4:104 cm:s−1; Sf = 0 cm:s−1; Dn = 27 cm2:s−1; H = 0:03 cm; Kl =5:6:10−7).

6

8

Fluences (P.cm−2)0.0 2.0 × 1011 4.0 × 1011 6.0 × 1011 8.0 × 1011 1.0 × 1012

Effici

ency

𝜂 (%

)

16

14

12

10

Figure 6: Efficiency versus fluences (L0 = 0:02 cm; Sb = 4:104 cm:s−1;Dn = 27 cm2:s−1; H = 0:03 cm; Kl = 5:6:10−7; Sf = 4:104 cm:s−1).

Table 1: Effect of the irradiation on the solar cell electricalparameters.

Ф (P.cm-2) Jsc(A.cm-2) Voc (V) Pm(W.cm-2) η %ð Þ

0 0.031176 0.60206 0.015561 15.561

109 0.030976 0.5996 0.015399 15.399

1010 0.029629 0.58653 0.014385 14.385

1011 0.025494 0.55851 0.011668 11.668

1012 0.020029 0.52351 0.00844926 6.589

6 International Journal of Photoenergy

Data Availability

The data used to support the findings of this study areavailable from the corresponding author upon request.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

The authors thank the International Science Program (ISP)for supporting their research group.

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