Opto-electrical surface engineering of wafer based c-Si solar cells Andrea Ingenito

203 Pages·2016·24.75 MB·English

Delft University of Technology

Opto-electrical surface engineering of wafer based c-Si solar cells
Ingenito, Andrea
DOI
10.4233/uuid:1cc31eff-4871-4d6f-8f32-8669257dc1ab
Publication date
2016
Document Version
Final published version
Citation (APA)
Ingenito, A. (2016). Opto-electrical surface engineering of wafer based c-Si solar cells.
https://doi.org/10.4233/uuid:1cc31eff-4871-4d6f-8f32-8669257dc1ab
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Opto-electrical surface engineering of wafer
based c-Si solar cells

Andrea Ingenito

Opto-electrical surface engineering of wafer
based c-Si solar cells

Proefschrift

ter verkrijging van de graad van doctor
aan de Technische Universiteit Delft,
op gezag van de Rector Magnificus prof. ir. K.C.A.M Luyben,
voorzitter van het College voor Promoties,
in het openbaar te verdedigen op 18 April 2016 om 10:00 uur

door

Andrea Ingenito

Master of Science, University of Naples Federico II
geboren te Salerno, Italy
This dissertation has been approved by the promotor:
prof. dr. M. Zeman

and

copromotor:
dr. O. Isabella

Composition of the doctoral committee:
Rector Magnificus, chairperson
prof. dr. M. Zeman, Technische Universiteit Delft, promotor
dr. O. Isabella, Technische Universiteit Delft, copromotor

Independent members:
prof. dr. A. Weeber Technische Universiteit Delft and ECN
dr. P. P. Altermatt Trina solar l.t.d.
prof. dr. J. Poortmans imec
dr. A. Poruba Institute of Physics, Academy of Sciences of
the Czech republic, v.v.i. and Fill Factory s.r.o.
prof. dr. S. W. Glunz Fraunhofer-Institut für Solare Energiesysteme
ISE

This thesis project was carried with a subsidy from the Dutch Ministry of
Economic Affairs under the EOS-LT program (Project No. EOSLT10037).

Copyright © 2016, Andrea Ingenito
Front and back cover is from a picture taken by Chantal Jimenez and designed
by Andrea Ingenito
Thesis printed by: CPI-Koninklijke Wöhrmann – Zutphen

All rights reserved.
No part of this material may be reproduced, stored in a retrieval system, nor
transmitted in any form or by any means without the prior written permission
of the copyright owner.

ISBN: 978-94-6328-033-4

A digital copy of this thesis is available at: http://repository.tudelft.nl
Per Ilaria, Chantal e
i miei genitori.

Contents

1. CHAPTER 1 .......................................................................................................................... 1
1.1 THE PROMISE OF PHOTOVOLTAICS ..................................................................................... 1
1.2 LIGHT MANAGEMENT IN C-SI SOLAR CELLS ....................................................................... 4
1.2.1 Light in-coupling ..................................................................................................... 5
1.2.2 Light scattering ........................................................................................................ 6
1.2.3 Internal rear reflectance .......................................................................................... 7
1.3 AIM OF THE THESIS.............................................................................................................. 8
1.4 OUTLINE OF THE THESIS ...................................................................................................... 9
1.5 MAIN CONTRIBUTIONS TO THE FIELD ............................................................................... 10
1.6 REFERENCES ...................................................................................................................... 11
2. CHAPTER 2 ........................................................................................................................ 15
2.1 WORKING PRINCIPLES OF C-SI SOLAR CELLS .................................................................... 15
2.2 SPECTRAL RESPONSE AND QUANTUM EFFICIENCY OF C-SI SOLAR CELL .......................... 18
2.3 EFFICIENCY LIMIT FOR SINGLE JUNCTION C-SI SOLAR CELLS ........................................... 19
2.4 MECHANISMS OF RECOMBINATION .................................................................................. 20
2.4.1 Radiative recombination ...................................................................................... 21
2.4.2 Auger recombination ............................................................................................ 21
2.4.3 Shockley-Read-Hall (SRH) recombination ....................................................... 22
2.4.4 Surface recombination .......................................................................................... 23
2.5 HISTORY OF C-SI SOLAR CELLS ......................................................................................... 24
2.5.1 History repeats itself: continuous swinging between n- and p-type wafer
based c-Si solar cells .............................................................................................................. 24
2.5.2 Mass production and laboratory scale p-type c-Si solar cells ....................... 25
2.5.2.1 Mass production p-type Al-BSF c-Si solar cells ....................................... 25
2.5.3 Laboratory scale p-type wafer based c-Si solar cells ....................................... 26
2.5.3.1 High efficiency p-type passivated emitter and rear solar cells ............. 26
2.5.3.2 Metal wrap through (MWT) p-type c-Si solar cells ................................. 27
2.5.3.3 Emitter wrap through (EWT) p-type c –Si solar cells ............................. 28
2.6 MASS PRODUCTION AND LABORATORY SCALE HIGH EFFICIENCY N-TYPE C-SI SOLAR
CELLS 28
2.6.1 Why n-type wafers? .............................................................................................. 28
2.6.2 Rear junction n-type solar cells............................................................................ 29
2.6.3 Front junction n-type solar cells .......................................................................... 29
2.6.4 Back contacted back junction c-Si solar cells ..................................................... 30
2.6.5 Passivating contacts for high efficiency c-Si solar cells ................................... 31
2.7 REFERENCES ...................................................................................................................... 32
3. CHAPTER 3 ......................................................................................................................... 39
3.1 ABSTRACT .......................................................................................................................... 39
3.2 INTRODUCTION ................................................................................................................. 40
3.3 OVERVIEW OF OPTO-ELECTRICAL DEVICE SIMULATORS FOR C-SI SOLAR CELLS .............. 41
3.3.1 The ASA device simulator .................................................................................... 43
3.4 STRUCTURE AND CHARACTERIZATION OF THE REFERENCE MC-SI SOLAR CELL .............. 44
3.5 CALIBRATION PROCEDURE ................................................................................................ 48
3.5.1 Optical modelling of front texture and anti-reflective coating ...................... 48
3.5.2 Opto-electrical modelling of the emitter ............................................................ 50
3.5.2.1 Modelling of SRH emitter recombination rate ......................................... 51
3.5.2.2 Modelling of Auger emitter recombination rate ...................................... 52
3.5.2.3 Modelling of Radiative emitter recombination rate ................................ 54
3.5.2.4 Optical modelling of the emitter ................................................................. 55
3.5.3 Opto-electrical modelling of the bulk mc-Si ..................................................... 55
3.5.4 Opto-electrical modelling of Al-BSF ................................................................... 56
3.6 RESULTS ............................................................................................................................. 60
3.6.1 Calibration results .................................................................................................. 60
3.6.2 Analysis of the optical and electrical losses of the calibrated mc-Si solar cell
62
3.7 OPTIMIZATION OF P-TYPE C-SI SOLAR CELL ..................................................................... 65
3.8 CONCLUSIONS ................................................................................................................... 69
3.9 APPENDIX .......................................................................................................................... 70
3.9.1 Optical constant Al-Si alloy .................................................................................. 70
3.10 REFERENCES .................................................................................................................. 72
4. CHAPTER 4 ......................................................................................................................... 79
4.1 ABSTRACT .......................................................................................................................... 79
4.2 INTRODUCTION ................................................................................................................. 80
4.3 FABRICATION AND CHARACTERIZATION ......................................................................... 81
4.3.1 Process flow description of advanced light trapping scheme ....................... 81
4.3.2 Characterization methods of the advanced light trapping scheme .............. 83
4.4 RESULTS AND DISCUSSIONS ............................................................................................... 84
4.4.1 Morphological analysis ......................................................................................... 84
4.4.2 Design of Distributed Bragg Reflector (DBR) ................................................... 85
4.4.3 Optical absorption of the advanced light trapping scheme .......................... 88
4.5 CONCLUSIONS ................................................................................................................... 94
4.6 APPENDIX .......................................................................................................................... 95
4.6.1 Optical modelling .................................................................................................. 95
4.7 REFERENCES ...................................................................................................................... 99
5. CHAPTER 5 ...................................................................................................................... 103
5.1 ABSTRACT ....................................................................................................................... 103
5.2 INTRODUCTION ............................................................................................................... 104
5.3 STRATEGY FOR FRONT SIDE PASSIVATION ...................................................................... 107
5.4 PROCESS FLOW DESCRIPTION .......................................................................................... 108
5.5 REAR GEOMETRY DEFINITION FOR THE FABRICATED IBC .............................................. 110
5.6 CHARACTERIZATION TOOLS ........................................................................................... 110
5.6.1 Theoretical background of QSSPC measurements ........................................ 111
5.6.2 Determination of J0s at high injection levels .................................................... 112
5.6.3 Determination of J0s at low injection levels. .................................................... 112
5.7 FABRICATION TOOLS ....................................................................................................... 113
5.7.1 Implantation of P-ions for FSF and BSF fabrication ...................................... 113
5.7.2 Epitaxial growth of in situ B-doped Si for emitter fabrication .................... 113
5.8 RESULTS AND DISCUSSIONS ............................................................................................ 114
5.8.1 Design of BSF and FSF ........................................................................................ 114
5.8.2 Design of epitaxially grown emitter................................................................. 117
5.8.3 Impact of FSF design on IBC solar cell performance .................................... 119
5.8.4 Impact of rear geometry on IBC solar cell performance .............................. 120
5.8.5 Analysis of the role of FSF in IBC c-Si solar cells ........................................... 122
5.9 ROADMAP FOR HIGH CONVERSION EFFICIENCY............................................................. 126
5.9.1 Optimization of implanted FSF......................................................................... 127
5.10 CONCLUSIONS ............................................................................................................. 128
5.11 REFERENCES ................................................................................................................ 129
6. CHAPTER 6 ...................................................................................................................... 135
6.1 ABSTRACT ....................................................................................................................... 135
6.2 INTRODUCTION ............................................................................................................... 136
6.3 FABRICATION AND CHARACTERIZATION ....................................................................... 137
6.3.1 Fabrication of advanced passivation scheme ................................................. 138
6.3.2 Fabrication of advanced light trapping scheme............................................. 138
6.3.3 Fabrication of IBC solar cells ............................................................................. 138
6.3.4 Samples characterization .................................................................................... 139