Titre : | Study of the type inversion of the semiconductor in irradiated solar cells |
Titre original: | Etude de l’inversion du type du semi-conducteur dans les cellules solaires irradiées |
Auteurs : | Abdelghani Hamache, Auteur ; Noureddine Sengouga, Directeur de thèse |
Type de document : | Thése doctorat |
Editeur : | Biskra [Algérie] : Faculté des Sciences Exactes et des Sciences de la Nature et de la Vie, Université Mohamed Khider, 2018 |
Format : | 1 vol. (130 p.) / 30 cm |
Langues: | Anglais |
Mots-clés: | Solar cells,Silicon,Irradiation,short circuit current,Type inversion,Numerical simulation,SCAPS. |
Résumé : |
Solar cells, used for space applications, are exposed to energetic particles such as protons and electrons. These energetic particles induce severe degradation on the performance of solar cells. This degradation is usually attributed to lattice damage in the active region of the solar cell. One of the phenomena observed in Silicon solar cells exposed to 1 MeV electron irradiation is the anomalous degradation of the short circuit current (Jsc). Itinitially decreases followed by a recovery before falling again with increasing electron fluence. This behaviour is usually attributed to type inversion of the semiconductor in thesolar cell active region. In order to elucidate this behaviour, a numerical simulation using SCAPS software is carried out. The current-voltage (J-V) characteristics of a Si n+-p-p+ structure are calculated under AM0 spectrum with the fluence of 1 MeV electrons as a variable parameter. The effect of irradiation on the solar cell is simulated by a set of defects of which the energy levels lie deep in energy gap of Silicon. Although several types of deep levels are induced by irradiation including deep donors, deep acceptors, and generation-recombination centres. It was found that the shallower donor trap is responsible for this behaviour and this not related to type inversion but to a lateral widening of the space charge region. It is also found that solar cells with smaller thickness have better radiation tolerance. |
Sommaire : |
Table of contents……………………………………………………...……………………vi List of Figures……………………………………………………...………………………xi List of tables……………………………………………………...……………………...xviii Introduction…………………………………………………...……………..……….........1 Chapter I: Physics of solar cells I.1. Introduction………………………………………………...……………………...........4 I.2. History of the solar cell……………………………………………………...…….……4 I.3. The physics of photovoltaic……………………………………………………...……..7 I.3.1. The photovoltaic effect……………………………………………………......7 I.3.2. Solar radiation spectrum………………………………………………...........7 I.3.3. Photon semiconductor interaction…………………………………………...10 I.4. the P-N junction……………………………………………………...………………..11 I.4.1. Current voltage characteristics of a diode…………………………………...13 I.4.2. Current voltage characteristics of the solar cell……………………………..14 I.4.2.1. Ideal solar cell……………………………………………………..14 I.4.2.2. Real solar cell……………………………………………………...16 I.5. Solar cell parameters (Solar Cell Figures of Merit) …………………………………..17 I.5.1. Short circuit current…………………………………………………….........17 I.5.2. Open circuit voltage……………………………………………………........18 I.5.3. Fill factor…………………………………………………………………….18 I.5.4. Efficiency……………………………………………………...…………….19 I.5.5. Spectral response and Quantum efficiency………………………………….19 I.6. Solar cell structure…………………………………………………………………….20 I.7. Materials used for solar cells………………………………………………………….22 I.7.1. Crystalline Silicon solar cells………………...……………………………...23 I.7.1.1. Mono-crystalline Silicon solar cells……………………………….23 I.7.1.1. Poly-crystalline Silicon solar cells………………………………...25 I.7.2. Thin films solar cells……………………………………………...…………26 Table of contents vii I.7.2.1.Amorphous Silicon solar cells………………………….......………26 I.7.2.2. Cadmium Telluride solar cells………………….…………………28 I.7.2.3.Copper Indium Gallium DiSelenide solar cells…....……….………28 I.7.3. Gallium-Arsenide (GaAs) solar cells………………..………………………29 I.7.4. Other semiconductor solar cells……………………………..………………30 I.7.4.1. Organic solar cells…………………………………………………31 I.7.4.2. Dye-Sensitized solar cells…………………………………………31 I.8. Materials used for space solar cells………………………………………………........32 Chapter II: Defects in semiconductor devices II.1. Introduction……………………………………………………....……………….......35 II.2. Semiconductors……………………………………………………...………….…….35 II.2.1. Intrinsic semiconductors……………………………………………..……..36 II.2.2. Extrinsic semiconductors……………………………………….…………..36 II.3. Types of defects in semiconductors (classification of defects)………………………36 II.3.1. Point defects………………………………………………………………...37 II.3.1.1. Vacancies……………………………………...………………….37 II.3.1.2. Substitutional defects……………………………………...……...38 II.3.1.3. Interstitials……………………………………...…………………38 II.3.1.4. Complexes of point defects……………….………………………39 a- Frenkel defects……………………………....…………………..39 b- Schottky defects…………………………………………………40 II.3.2. Line defects……………………………………………...………………….40 II.3.2.1. Edge dislocation……………………………………...…………...40 II.3.2.2. Screw dislocation……………………………………...………….41 II.3.3. Planar defects (two dimensional defects)..…………………………………42 II.3.3.1 Stacking faults………….………………………………………….42 II.3.3.2 Grain boundaries…………………………………………………..42 II.3.4. Spatial (volume) defects……………………………………………………43 a) Precipitates……………………………………...……………………….43 b) Dispersants…………………………………………………...…………43 c) Inclusions………………………………………………………...…...…43 d) Voids……………………………………………………………....……44 Table of contents viii II.4. Defects and their electronic states……………………………………………………44 II.4.1. Shallow defects……………………………………………………..………44 II.4.2. Deep defects………………………………………………………………...45 II.4.2.1. Emission and capture of carriers from deep levels……….………46 Chapter III: Space environment and its effects on solar cells III.1. Introduction…………………………………………………….................................51 III.2. Sources of radiation in space………………………………………………………...51 III.2.1. Solar wind………………………………………………..………………...52 III.2.2. Solar flares………………………………………………………...……….53 III.2.3. Cosmic rays……………………………………………..…………………53 III.2.4. Trapped particles in Van Allen Belts……………………...………………54 III.3. Classification of orbits in a space mission…………………………………………..56 III.3.1. Low earth orbit (LEO) …………………………………….………………56 III.3.2. Medium earth orbit (MEO) ……………………………………………….56 III.3.3. Geostationary earth orbit (GEO) ………………………….………………57 III.4. Radiation Interaction with matter……………………………………………………58 III.4.1. Photon interactions………………………………………………………...58 III.4.1.1. Photo-electric effect………………………………………...……58 III.4.1.2. Compton scattering………………………………………………59 III.4.1.3. Pair production……………………………………………...……60 III.4.2. Charged particle interaction……………………..…………………………61 III.5. Effects of radiation on solar cells……………………………………………………63 III.5.1. Ionization……………………………………………..................................63 III.5.2. Displacement damage……………………….………………………..........64 III.6. Defects induced by radiation………………………………...………………………65 III.6.1. Defects induced in Silicon solar cells…………………………………...…66 Chapter IV: Simulation of solar cells and SCAPS Simulator IV.1. Introduction…………………………………………………….................................69 IV.2. Physical basis for semiconductor device modelling………………………………...69 IV.2.1. Semiconductors at thermal equilibrium…………………………………...69 IV.2.1.1. Carrier concentration……………………………………….........70 Table of contents ix IV.2.1.2. Intrinsic carrier concentration……………………………………71 IV.2.1.3. Donors and acceptors………………………………………........72 IV.2.2. Non-equilibrium carrier concentration……………………….……………73 IV.2.3. Basis equations for semiconductor modelling…………………………….74 IV.2.3.1. Poisson’s equation…………….…………………………............74 IV.2.3.2. Continuity equations………….…………………………….........75 IV.2.3.3. Current-density equations…...……………………………….......75 IV.2.4. Optical generation of electron-hole pairs…………………….........………76 IV.2.5. Recombination’s phenomenon in semiconductors…...................................77 IV.2.5.1. Radiative recombination…..……........………………………......77 IV.2.5.2. Auger recombination…….………………………........…………78 IV.2.5.3. Shockley-Read-Hall recombination (SRH) .………….....………78 IV.3. SCAPS simulator………………………………………............................................79 IV.3.1. General overview and simulation method……………........................……79 IV.3.2. Action panel…………………………………............................…….........80 IV.3.3. Solar cell definition…………………………….................………….........81 IV.3.4. Define the working point…………….........………………………….........84 IV.3.5. Defects and recombination……………......………………………….........84 IV.3.6. Select the measurements to simulate…………………………...…….........85 IV.3.6. Calculate and display the simulated curves…………………..................…85 Chapter V: Results and Discussions V.1. Introduction………………………………………......................................................86 V.2. Previous works and aim of the study………………………………………................87 V.3. Silicon solar cell structure and physical parameters used in this work………............89 V.4. Defects induced by irradiation………………………………………..........................90 V.5. Simulation results before irradiation………………………………………................91 V.6. Simulation results after 1 MeV electron irradiation………………………………….92 V.6.1. Effect of the deeper donor trap ( ) …………………………...92 V.6.2. Effect of the shallower donor trap ( ……………......……….96 V.6.3. Effect of the two donor traps…………………………………...…..............99 V.6.4. Summary…………………………………...…...........................................100 V.7. Changing the parameters of the defects…………………………………...…...........100 Table of contents x V.7.1. The deeper donor trap ( ) …………………………………...100 V.7.2. The shallower donor trap ( ………………………………..105 V.8. Study of the type inversion………………..…………….……...…...........................110 V.9. The effect of the cell structure…………………………………...….........................114 V.9.1. The effect of the base carrier concentration…………………………...….114 V.9.2. The effect of the cell thickness…………………………...….....................115 Conclusion…………………………………..…...............................................................118 References…………………...…….………..…...............................................................121 |
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