<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE article  PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "http://dtd.nlm.nih.gov/publishing/3.0/journalpublishing3.dtd"><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" dtd-version="3.0" xml:lang="en" article-type="research article"><front><journal-meta><journal-id journal-id-type="publisher-id">EPE</journal-id><journal-title-group><journal-title>Energy and Power Engineering</journal-title></journal-title-group><issn pub-type="epub">1949-243X</issn><publisher><publisher-name>Scientific Research Publishing</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.4236/epe.2020.121001</article-id><article-id pub-id-type="publisher-id">EPE-97560</article-id><article-categories><subj-group subj-group-type="heading"><subject>Articles</subject></subj-group><subj-group subj-group-type="Discipline-v2"><subject>Engineering</subject></subj-group></article-categories><title-group><article-title>
 
 
  Electrical Parameters Determination from Base Thickness Optimization in a Silicon Solar Cell under Influence of the Irradiation Energy Flow of Charged Particles
 
</article-title></title-group><contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Ousmane</surname><given-names>Sow</given-names></name><xref ref-type="aff" rid="aff1"><sup>1</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Mamadou</surname><given-names>Lamine Ba</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Mohamed</surname><given-names>Abderrahim Ould El Moujtaba</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Youssou</surname><given-names>Traore</given-names></name><xref ref-type="aff" rid="aff3"><sup>3</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>El</surname><given-names>Hadji Sow</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Cheikh</surname><given-names>Tidiane Sarr</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Masse</surname><given-names>Samba Diop</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Grégoire</surname><given-names>Sissoko</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib></contrib-group><aff id="aff3"><addr-line>Ecole Polytechnique de Thiès, Thiès, Sénégal</addr-line></aff><aff id="aff1"><addr-line>University Institute of Technology, University of Thiès, Thiès, Sénégal</addr-line></aff><aff id="aff2"><addr-line>Laboratory of Semiconductors and Solar Energy, Physics Department, Faculty of Science and Technology, University Cheikh Anta Diop, Dakar, Senegal</addr-line></aff><pub-date pub-type="epub"><day>30</day><month>12</month><year>2019</year></pub-date><volume>12</volume><issue>01</issue><fpage>1</fpage><lpage>15</lpage><history><date date-type="received"><day>29,</day>	<month>October</month>	<year>2019</year></date><date date-type="rev-recd"><day>28,</day>	<month>December</month>	<year>2019</year>	</date><date date-type="accepted"><day>31,</day>	<month>December</month>	<year>2019</year></date></history><permissions><copyright-statement>&#169; Copyright  2014 by authors and Scientific Research Publishing Inc. </copyright-statement><copyright-year>2014</copyright-year><license><license-p>This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/</license-p></license></permissions><abstract><p>
 
 
  In this work, we study the characteristics I-V and P-V of a silicon solar cell as well as its fill factor, its electrical power from the optimum thickness obtained in the base under variation of the irradiation energy flow of charged particles. The recombination velocity at the junction corresponding to the maximum power point was also deduced.
 
</p></abstract><kwd-group><kwd>Silicon Solar Cell</kwd><kwd> Flow Irradiation Energy</kwd><kwd> Recombination Velocity</kwd><kwd>  Optimum Base Thickness</kwd></kwd-group></article-meta></front><body><sec id="s1"><title>1. Introduction</title><p>Authors have studied the electrical parameters of the solar cell namely the fill factor, the conversion efficiency, the power, the I-V and P-V characteristics under the Influence of Irradiation [<xref ref-type="bibr" rid="scirp.97560-ref1">1</xref>], from the back surface recombination velocity modeling in white biased [<xref ref-type="bibr" rid="scirp.97560-ref2">2</xref>], under temperature with the junction surface recombination concept [<xref ref-type="bibr" rid="scirp.97560-ref3">3</xref>], by acquisition automatic of I-V properties and temperature [<xref ref-type="bibr" rid="scirp.97560-ref4">4</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref5">5</xref>], under influence of incidence angle on a vertical Silicon Solar [<xref ref-type="bibr" rid="scirp.97560-ref6">6</xref>], by illumination wavelength effect on a parallel vertical junction silicon solar cell and under irradiation [<xref ref-type="bibr" rid="scirp.97560-ref7">7</xref>] and illumination level effects on macroscopic parameters of a bifacial solar cell [<xref ref-type="bibr" rid="scirp.97560-ref8">8</xref>].</p><p>Our study is to determinate these electrical parameters from the optimal base thickness of the solar cell under variation of the irradiation energy flow and extracting the values of the recombination velocity at the junction, corresponding to the maximum power.</p></sec><sec id="s2"><title>2. Presentation of the Solar Cell</title><p><xref ref-type="fig" rid="fig1">Figure 1</xref> represents a n<sup>+</sup>-p-p<sup>+</sup> silicon solar cell [<xref ref-type="bibr" rid="scirp.97560-ref9">9</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref10">10</xref>]. The emitter is the thin (n<sup>+</sup>) zone covered by the front grids. Then comes the space charge region (SCR), which is formed by migration of the majority charges coming from the two semiconductors (n<sup>+</sup> and p), according to the principle of Helmotz or compensation law. They are formed as fixed charges that delimit a space, where there is an intense electric field, which will allow the dissociation of photogenerated electron-hole pairs, and their acceleration to the deficit areas in corresponding charge. The (p) zone is doped with boron atoms and represents the larger thickness base (170 - 300 &#181;m). It is the zone of pair creation (electron-hole), the most important, which justifies, the interest of its study in a solar cell. The (p<sup>+</sup>) zone over doped in boron atoms, allows the creation of another rear space charge region, where the created electric field (Back surface Field) will allow the minority carriers of the (p) zone to be pushed back to the junction, to be then collected and participated in the photocurrent.</p></sec><sec id="s3"><title>3. Theory</title><p>The solar cell thus achieved (<xref ref-type="fig" rid="fig1">Figure 1</xref>) is previously subjected to a flow of charged particles ( ϕ p ) and intensity (kl) [<xref ref-type="bibr" rid="scirp.97560-ref11">11</xref>], allowing to simulate the conditions of operation outside the atmosphere, in the supply of satellites. Under polychromatic illumination, the density of charge carriers δ ( x , ϕ p , k l ) generated at point of abscissa x in the base, according to the law is defined by equation (Equation (1)), describing the generation rate [<xref ref-type="bibr" rid="scirp.97560-ref12">12</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref13">13</xref>] and expressed as:</p><p>G ( x ) = n &#215; ∑ i = 1 3 a i &#215; e − b i ⋅ x (1)</p><p>δ ( x , ϕ p , k l ) follows the charge transport equation given by (Equation (2)):</p><p>D ( k l , ϕ p ) ∂ 2 δ ( x , k l , ϕ p ) ∂ x 2 − δ ( x , k l , ϕ p ) τ + G ( x ) = 0 (2)</p><p>It is accompanied by the Equation (3) and Equation (4) specifying the conditions at the (p) base boundaries in the 1D model, which define, the Sf [<xref ref-type="bibr" rid="scirp.97560-ref14">14</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref15">15</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref16">16</xref>] and Sb [<xref ref-type="bibr" rid="scirp.97560-ref17">17</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref18">18</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref19">19</xref>] recombination velocity rates, respectively at the junction (n<sup>+</sup>/p) at x = 0, and in the rear (p/p), at x = H.</p><p>D ( k l , ϕ p ) ∂ δ ( x , k l , ϕ p ) ∂ x | x = 0 = S f &#215; δ ( 0 , k l , ϕ p ) (3)</p><p>D ( k l , ϕ p ) ∂ δ ( x , k l , ϕ p ) ∂ x | x = H = − S b &#215; δ ( H , k l , ϕ p ) (4)</p><p>The diffusion term influenced by the irradiation conditions of the solar cell, is given by the following empirical relationship [<xref ref-type="bibr" rid="scirp.97560-ref11">11</xref>]:</p><p>L ( k l , ϕ p ) = 1 ( 1 L 0 2 + k l &#215; ϕ p ) 1 / 2 (5)</p><p>where:</p><p>L 0 is the diffusion length of the excess minority carriers in absence of irradiation energy flux ( ϕ p ). L ( k l , ϕ p ) is the diffusion length of the excess minority carrier in the base as a function of the irradiation energy flux ( ϕ p ) and the damage coefficient intensity (kl) and which may be related to Einstein’s relationship by:</p><p>[ L ( k l , ϕ p ) ] 2 = τ &#215; D ( k l , ϕ p ) (6)</p><p>D ( k l , ϕ p ) and τ are respectively the diffusion coefficient and lifetime of the electrons in the base of the solar cell under irradiation.</p><p>The continuity Equation (2) solution is provided by:</p><p>δ ( x , k l , ϕ p ) = A &#215; cosh [ x L ( k l , ϕ p ) ] + B &#215; sinh [ x L ( k l , ϕ p ) ] + ∑ K i &#215; e − b i ⋅ x (7)</p><p>where, coefficients A and B, will be obtained by use of Equation (3) and Equation (4).</p></sec><sec id="s4"><title>4. Results and Discussion</title><sec id="s4_1"><title>4.1. Expressions of Photocurrent, Recombination Velocity (Sb) and Phototension</title><p>1) Fick’s charged particle law establishes the photocurrent density of minority carriers, derived from the base by the following relationship:</p><p>J p h ( S f , H , k l , ϕ p ) = q ⋅ D ( k l , ϕ p ) ⋅ [ ∂ δ ( S f , x , H , k l , ϕ p ) ∂ x ] x = 0 = q ⋅ D ( k l , ϕ p ) B ( S f , H , k l , ϕ p ) L ( k l , ϕ p ) + ∑ i = 1 3 K i ⋅ b i (8)</p><p>2) At the high values of recombination velocity at the junction, it is established that [<xref ref-type="bibr" rid="scirp.97560-ref16">16</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref19">19</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref20">20</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref21">21</xref>]:</p><p>[ ∂ J p h ( S f , k l , ϕ p ) ∂ S f ] S f ≻ 5 &#215; 10 5 cm ⋅ s − 1 = 0 (9)</p><p>Derived from this equation, it gives the following relations:</p><p>i) S b 0 ( H , k l , ϕ p ) L ( k l , ϕ p ) D ( k l , ϕ p ) = − tanh ( H L ( k l , ϕ p ) ) (10)</p><p>Equation (10), gives rise the definition of intrinsic velocity and becomes a diffusion velocity [<xref ref-type="bibr" rid="scirp.97560-ref19">19</xref>], when H is very large compared to L.</p><p>ii) S b 1 ( H , k l , ϕ p ) L ( k l , ϕ p ) D ( k l , ϕ p ) = ∑ i = 1 3 L ( k l , ϕ p ) &#215; b i &#215; ( e b i ⋅ H − cosh ( H L ( k l , ϕ p ) ) ) − sinh ( H L ( k l , ϕ p ) ) − L ( k l , ϕ p ) &#215; b i &#215; sinh ( H L ( k l , ϕ p ) ) + cosh ( H L ( k l , ϕ p ) ) − e b i ⋅ H (11)</p><p>Equation (11) is marked by a term of absorption (b<sub>i</sub>) and leads to generation velocity, when H is small compared to L [<xref ref-type="bibr" rid="scirp.97560-ref19">19</xref>].</p><p>3) By Boltzmann’s law, the photovoltage at the junction is written as:</p><p>V p h ( S f , H , k l , ϕ p ) = K b &#215; T q ⋅ ln ( N b n i 2 ⋅ δ ( 0 , H , k l , ϕ p ) + 1 ) (12)</p><p>where, Kb is the Boltzmann constant, q is the elementary charge of the electron and T is the temperature. Nb is the solar cell base doping rate, and n<sub>i</sub> is the intrinsic density of minority charge carriers.</p></sec><sec id="s4_2"><title>4.2. Optimum Thickness of the Base, Deduced from Each Case of Irradiation Flow</title><p>The expressions (Equation (10) and Equation (11)) are represented by the <xref ref-type="fig" rid="fig2">Figure 2</xref>, allowing to obtain the optimum thickness (abscissa of intercept point) of the base [<xref ref-type="bibr" rid="scirp.97560-ref22">22</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref23">23</xref>] for different cases of irradiation of the solar cell, and presented by <xref ref-type="table" rid="table1"><xref ref-type="table" rid="table">Table </xref>1</xref>. These results are decisive for the characterization of the solar cell under irradiation, through the calculation of photocurrent density, photovoltage and conversion efficiency.</p></sec><sec id="s4_3"><title>4.3. J p h ( S f , ϕ p , H o p t ) - V ( S f , ϕ p , H o p t ) Characteristic</title><p>The profile of the J p h ( S f , ϕ p , H o p t ) - V ( S f , ϕ p , H o p t ) characteristic for different values of the irradiation energy flow and base optimum thickness is shown in <xref ref-type="fig" rid="fig3">Figure 3</xref>. We note that the photocurrent density ( J ( S f , ϕ p , H o p t ) ) decreases</p><table-wrap id="table1" ><label><xref ref-type="table" rid="table1"><xref ref-type="table" rid="table">Table </xref>1</xref></label><caption><title> Base optimum thickness values obtained for different irradiation energy flow</title></caption><table><tbody><thead><tr><th align="center" valign="middle" >ϕ p (MeV)</th><th align="center" valign="middle" >60</th><th align="center" valign="middle" >80</th><th align="center" valign="middle" >100</th><th align="center" valign="middle" >120</th><th align="center" valign="middle" >140</th></tr></thead><tr><td align="center" valign="middle" >Hopt (&#181;m)</td><td align="center" valign="middle" >127</td><td align="center" valign="middle" >123</td><td align="center" valign="middle" >120</td><td align="center" valign="middle" >117</td><td align="center" valign="middle" >114</td></tr></tbody></table></table-wrap><p>with the increase of the irradiation energy flow. And the photovoltage increases slightly.</p></sec><sec id="s4_4"><title>4.4. Electrical Power of the Solar Cell</title><p><xref ref-type="fig" rid="fig4">Figure 4</xref> represents the equivalent electric circuit of an illuminated solar cell [<xref ref-type="bibr" rid="scirp.97560-ref9">9</xref>].</p><p>The Ohm law applied to the circuit in <xref ref-type="fig" rid="fig4">Figure 4</xref> yields the electric power delivered by the base of the solar cell to an external load as follows:</p><p>P ( S f , k l , ϕ p ) = V p h ( S f , k l , ϕ p ) &#215; J ( S f , k l , ϕ p ) (13)</p><p>with:</p><p>J ( S f , k l , ϕ p ) = J p h ( S f , k l , ϕ p ) − J d ( S f , k l , ϕ p ) (14)</p><p>where J<sub>d</sub> is the solar cell density of current under dark expressed as:</p><p>J d ( S f , k l , ϕ p ) = q &#215; S f 0 &#215; n i 2 N b &#215; exp ( V p h ( S f , k l , ϕ p ) V T − 1 ) (15)</p><p>Sf<sub>0</sub> is the excess minority carrier recombination velocity associated with shunt resistance-induced charge carrier losses [<xref ref-type="bibr" rid="scirp.97560-ref24">24</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref25">25</xref>], which characterizes the quality of the solar cell [<xref ref-type="bibr" rid="scirp.97560-ref15">15</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref16">16</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref20">20</xref>]. The expression intrinsic recombination velocity at the junction is given in static regime [<xref ref-type="bibr" rid="scirp.97560-ref26">26</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref27">27</xref>] and under polychromatic illumination, by [<xref ref-type="bibr" rid="scirp.97560-ref28">28</xref>] and applied her for solar cell under irradiation as:</p><p>S f 0 ( k l , ϕ p ) = ∑ i = 1 3 K i &#215; D ( k l , ϕ p ) &#215; [ b i &#215; L ( k l , ϕ p ) − e − b i &#215; H &#215; ( s h ( H L ( k l , ϕ p ) ) + b i &#215; L ( k l , ϕ p ) &#215; c h ( H L ( k l , ϕ p ) ) ) ] L ( k l , ϕ p ) &#215; [ e − b i &#215; H &#215; ( c h ( H L ( k l , ϕ p ) ) + b i &#215; L ( k l , ϕ p ) &#215; s h ( H L ( k l , ϕ p ) ) ) − 1 ] (16)</p></sec><sec id="s4_5"><title>4.5. P ( S f , ϕ p , H o p t ) - V ( S f , ϕ p , H o p t ) Characteristic</title><p><xref ref-type="fig" rid="fig5">Figure 5</xref> and <xref ref-type="fig" rid="fig6">Figure 6</xref> show the variations in electrical power as function of both, the excess minority carrier recombination velocity at the junction and the photovoltage for different irradiation energy flow and optimum base thickness.</p><p>We note on <xref ref-type="fig" rid="fig5">Figure 5</xref>, the decrease of maximum power amplitude with the irradiation energy flow corresponding the base thickness.</p><p>On <xref ref-type="fig" rid="fig6">Figure 6</xref>, it is also observed a decrease in power with the increase of irradiation energy flow corresponding the optimum base thickness.</p></sec><sec id="s4_6"><title>4.6. Fill Factor and Efficiency</title><sec id="s4_6_1"><title>4.6.1. Fill Factor</title><p>The fill factor is an important parameter for a solar cell. It shows the physical quality of the solar cell for a conversion efficiency and indicates the performance of a perfect cell. The expression of the fill factor is given [<xref ref-type="bibr" rid="scirp.97560-ref29">29</xref>] as:</p><p>F F = P max V O C &#215; J S C (17)</p><p>P<sub>max</sub> is the maximum power. Voc is the open circuit photovoltage.</p><p>J<sub>sc</sub> is the short circuit current density</p></sec><sec id="s4_6_2"><title>4.6.2. Efficiency</title><p>The conversion efficiency of a solar cell is the ratio between the maximum power supplied provided by the solar cell and the power of absorbed illumination. It is written as follows:</p><p>η = J S C max &#215; V max P i n c i d e n t (18)</p><p>P i n c i d e n t is the incident light power absorbed by the solar cell.</p><p>With: P i n c i d e n t = 100   mW ⋅ cm − 2 in the standard conditions (Air Mass 1.5).</p><p>The obtained solar cell fill factor and efficiency for different irradiation energy flow values corresponding to the optimum thickness are shown in <xref ref-type="table" rid="table2"><xref ref-type="table" rid="table">Table </xref>2</xref>.</p></sec><sec id="s4_6_3"><title>4.6.3. Curves of Power and Efficiency</title><p><xref ref-type="fig" rid="fig7">Figure 7</xref> represents the profil of the power versus irradiation energy, <xref ref-type="fig" rid="fig8">Figure 8</xref> and <xref ref-type="fig" rid="fig9">Figure 9</xref> represent the profils of the power and the efficiency versus the optimum base thickness.</p><table-wrap id="table2" ><label><xref ref-type="table" rid="table2"><xref ref-type="table" rid="table">Table </xref>2</xref></label><caption><title> <xref ref-type="table" rid="table">Table </xref>of parameters leading to the fill factor and efficiency corresponding to the optimum base thickness for different irradiation energy flow</title></caption><table><tbody><thead><tr><th align="center" valign="middle" >ϕ p (MeV)</th><th align="center" valign="middle" >60</th><th align="center" valign="middle" >80</th><th align="center" valign="middle" >100</th><th align="center" valign="middle" >120</th><th align="center" valign="middle" >140</th></tr></thead><tr><td align="center" valign="middle" >Hopt (cm)</td><td align="center" valign="middle" >0.0127</td><td align="center" valign="middle" >0.0123</td><td align="center" valign="middle" >0.0120</td><td align="center" valign="middle" >0.0117</td><td align="center" valign="middle" >0.0114</td></tr><tr><td align="center" valign="middle" >J<sub>sc</sub><sub>max</sub> (A/cm<sup>2</sup>)</td><td align="center" valign="middle" >0.0295</td><td align="center" valign="middle" >0.0263</td><td align="center" valign="middle" >0.0242</td><td align="center" valign="middle" >0.0224</td><td align="center" valign="middle" >0.0212</td></tr><tr><td align="center" valign="middle" >J<sub>d</sub> (Sf<sub>max</sub>) (A/cm<sup>2</sup>)</td><td align="center" valign="middle" >0.1374 &#215; 10<sup>−3</sup></td><td align="center" valign="middle" >0.1355 &#215; 10<sup>−3</sup></td><td align="center" valign="middle" >0.1342 &#215; 10<sup>−3</sup></td><td align="center" valign="middle" >0.1330 &#215; 10<sup>−3</sup></td><td align="center" valign="middle" >0.1318 &#215; 10<sup>−3</sup></td></tr><tr><td align="center" valign="middle" >V<sub>max</sub> (V)</td><td align="center" valign="middle" >0.5931</td><td align="center" valign="middle" >0.5940</td><td align="center" valign="middle" >0.5946</td><td align="center" valign="middle" >0.5951</td><td align="center" valign="middle" >0.5955</td></tr><tr><td align="center" valign="middle" >P<sub>max</sub> (W/cm<sup>2</sup>)</td><td align="center" valign="middle" >0.01741</td><td align="center" valign="middle" >0.01554</td><td align="center" valign="middle" >0.01431</td><td align="center" valign="middle" >0.01325</td><td align="center" valign="middle" >0.01254</td></tr><tr><td align="center" valign="middle" >FF</td><td align="center" valign="middle" >0.9951</td><td align="center" valign="middle" >0.9947</td><td align="center" valign="middle" >0.9945</td><td align="center" valign="middle" >0.9939</td><td align="center" valign="middle" >0.9933</td></tr><tr><td align="center" valign="middle" >η<sub>max</sub> (%)</td><td align="center" valign="middle" >17.41</td><td align="center" valign="middle" >15.54</td><td align="center" valign="middle" >14.31</td><td align="center" valign="middle" >13.25</td><td align="center" valign="middle" >12.55</td></tr></tbody></table></table-wrap><p>The equation obtained from the power versus the irradiation energy is given by the following relation:</p><p>P max = u &#215; ϕ p 2 − w &#215; ϕ p + z (19)</p><p>with: u = 4 &#215; 10 − 7 W ⋅ cm − 2 / MeV , w = 10 − 4 W ⋅ cm − 2 / MeV , z = 0.0247   W / cm 2</p><p>The equation obtained from the power versus the base thickness is given by the following relation:</p><p>P max = α &#215; H 2 − β &#215; H + ν (20)</p><p>with: α = 1140.6   W / cm 4 , β = 23.709   W / cm 3 , ν = 0.1346   W / cm 2</p><p>The fit equation obtained from the efficiency versus the base thickness is given by the following relation:</p><p>η max = m &#215; H 2 − n &#215; H + k (21)</p><p>with: m = 10 6 cm − 2 , n = 24038   cm − 1 , k = 136.58</p><p>We note on <xref ref-type="fig" rid="fig8">Figure 8</xref> and <xref ref-type="fig" rid="fig9">Figure 9</xref> that the power and the efficiency increase with the increasing base thickness.</p></sec></sec><sec id="s4_7"><title>4.7. Recombination Velocity Sfmax at the Junction</title><p>Sf<sub>max</sub>, the excess minority carrier recombination velocity at the junction corresponding to the maximum power point is point out by solving the following equation [<xref ref-type="bibr" rid="scirp.97560-ref3">3</xref>] [<xref ref-type="bibr" rid="scirp.97560-ref30">30</xref>].</p><p>∂ P ∂ S f = 0 (22)</p><p>From this Equation (22), the transcendental equation depending on recombination velocity Sf and the irradiation energy is obtained, for each Hopt. It is given by the following expressions:</p><p>M ( S F max , k l , ϕ p ) = 1 S F max &#215; L ( k l , ϕ p ) &#215; [ 1 − S F max &#215; L ( k l , ϕ p ) Y 1 &#215; D ( k l , ϕ p ) + S F max &#215; L ( k l , ϕ p ) ] (23)</p><p>N ( S F max , k l , ϕ p ) = [ Γ max ( 0 , k l , ϕ p ) ( Γ max ( 0 , k l , ϕ p ) + n i 2 N b ) &#215; ( S F max &#215; L ( k l , ϕ p ) + Y 1 &#215; D ( k l , ϕ p ) ) ]       &#215; [ 1 log ( N b &#215; Γ max ( 0 , k l , ϕ p ) n i 2 + 1 ) ] (24)</p><p>Γ max ( 0 , k l , ϕ p ) is the density of the minority excess minority carrier at the point of maximum power, its expression is given by the following relations:</p><p>Γ max ( 0 , k l , ϕ p ) = β &#215; D ( k l , ϕ p ) &#215; [ Y 2 + Y 1 − b i &#215; L ( k l , ϕ p ) S F max &#215; L ( k l , ϕ p ) + Y 1 &#215; D ( k l , ϕ p ) ] (25)</p><p>with:</p><p>β = − a i &#215; L ( k l , ϕ p ) 2 &#215; n D ( k l , ϕ p ) &#215; ( L ( k l , ϕ p ) 2 &#215; b i 2 − 1 ) (26)</p><p>Y 1 = D ( k l , ϕ p ) L ( k l , ϕ p ) &#215; sinh ( H L ( k l , ϕ p ) ) + S b ( k l , ϕ p ) &#215; cosh ( H L ( k l , ϕ p ) ) D ( k l , ϕ p ) L ( k l , ϕ p ) &#215; cosh ( H L ( k l , ϕ p ) ) + S b ( k l , ϕ p ) &#215; sinh ( H L ( k l , ϕ p ) ) (27)</p><p>Y 2 = ( D ( k l , ϕ p ) &#215; b i − S b ( k l , ϕ p ) ) &#215; exp ( − b i ⋅ H ) D ( k l , ϕ p ) L ( k l , ϕ p ) &#215; cosh ( H L ( k l , ϕ p ) ) + S b ( k l , ϕ p ) &#215; sinh ( H L ( k l , ϕ p ) ) (28)</p><p>The graphical resolution of this transcendental equation as a function of the excess minority carrier recombination velocity Sf at the junction [<xref ref-type="bibr" rid="scirp.97560-ref30">30</xref>], for different irradiation energy flow corresponding the optimum base thickness, gives the Sf<sub>max</sub> values by the intercept point of the two curves represented by <xref ref-type="fig" rid="fig1">Figure 1</xref>0.</p><p>The results obtained from <xref ref-type="fig" rid="fig1">Figure 1</xref>0 corresponding to the numerical values of Sf<sub>max</sub>, are given in <xref ref-type="table" rid="table">Table </xref>3.</p><p>The recombination velocity Sf<sub>max</sub> of the excess minority carrier at the junction yielding P<sub>max</sub>, decreases while irradiation energy flow increases.</p>Curve Sf<sub>max</sub>(H<sub>opt</sub>)<p><xref ref-type="fig" rid="fig1">Figure 1</xref>1 represents the profil of the recombination velocity Sf<sub>max</sub> of the excess minority carrier at the junction yielding P<sub>max</sub>, as function of optimum base thickness.</p><table-wrap id="table3" ><label><xref ref-type="table" rid="table">Table </xref>3</label><caption><title> The numerical values of Sf<sub>max</sub> for different irradiation energy flow and the optimum base thickness</title></caption><table><tbody><thead><tr><th align="center" valign="middle" >Irradiation energy (MeV)</th><th align="center" valign="middle" >Base thickness (cm)</th><th align="center" valign="middle" >Intercept points curves (p)</th><th align="center" valign="middle" >Sfmax (p∙10<sup>p</sup> cm/s)</th></tr></thead><tr><td align="center" valign="middle" >60</td><td align="center" valign="middle" >0.0127</td><td align="center" valign="middle" >1.9683</td><td align="center" valign="middle" >182.975</td></tr><tr><td align="center" valign="middle" >80</td><td align="center" valign="middle" >0.0123</td><td align="center" valign="middle" >1.9638</td><td align="center" valign="middle" >180.675</td></tr><tr><td align="center" valign="middle" >100</td><td align="center" valign="middle" >0.0120</td><td align="center" valign="middle" >1.9600</td><td align="center" valign="middle" >178.754</td></tr><tr><td align="center" valign="middle" >120</td><td align="center" valign="middle" >0.0117</td><td align="center" valign="middle" >1.9564</td><td align="center" valign="middle" >176.953</td></tr><tr><td align="center" valign="middle" >140</td><td align="center" valign="middle" >0.0114</td><td align="center" valign="middle" >1.9534</td><td align="center" valign="middle" >175.465</td></tr></tbody></table></table-wrap><p>The equation obtained from the best fit of Sf<sub>max</sub> versus base optimum thickness is given by the following relation:</p><p>S f max = a &#215; H O p t + b (29)</p><p>with: a = 5859.6   s − 1 , b = 108.53   cm ⋅ s − 1</p><p>The recombination velocity Sf<sub>max</sub> of the excess minority carrier at the junction increases with the optimum base thickness.</p></sec></sec><sec id="s5"><title>5. Conclusion</title><p>In this work, a technique for obtaining the optimum thickness of the solar cell under variation of the irradiation energy flow has been presented. It is also deduced from this optimal thickness, the fill factor, the electrical power, the efficiency of the solar cell as well as the recombination velocity at the junction through a transcendental equation, leading to maximum power. We found that the electrical parameters of the solar cell decrease with the increasing of the irradiation energy flow. Then we have plotted and fitted the curves of the power, the efficiency and the recombination velocity (at the maximum power) versus the optimum base thickness.</p></sec><sec id="s6"><title>Conflicts of Interest</title><p>The authors declare no conflicts of interest regarding the publication of this paper.</p></sec><sec id="s7"><title>Cite this paper</title><p>Sow, O., Ba, M.L., El Moujtaba, M.A.O., Traore, Y., Sow, El.H., Sarr, C.T., Diop, M.S. and Sissoko, G. (2020) Electrical Parameters Determination from Base Thickness Optimization in a Silicon Solar Cell under Influence of the Irradiation Energy Flow of Charged Particles. Energy and Power Engineering, 12, 1-15. https://doi.org/10.4236/epe.2020.121001</p></sec></body><back><ref-list><title>References</title><ref id="scirp.97560-ref1"><label>1</label><mixed-citation publication-type="other" xlink:type="simple">Ould El Moujtaba, M.A., Ndiaye, M., Diao, A., Thiame, M., Barro, I.F. and Sissoko, G. (2012) Theoretical Study of the Influence of Irradiation on a Silicon Solar Cell under Multispectral Illumination. Research Journal of Applied Sciences, Engineering and Technology, 4, 5068-5073.</mixed-citation></ref><ref id="scirp.97560-ref2"><label>2</label><mixed-citation publication-type="other" xlink:type="simple">Diasse, O., Diao, A., Wade, M., Diouf, M.S., Diatta, I., Mane, R., Traore, Y. and Sissoko, G. 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