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Oxide and Composite Electron Transport Layers for Efficient Dye-Sensitized Solar Cells

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Oxide and Composite Electron Transport Layers for Efficient Dye-Sensitized Solar Cells Université Pierre et Marie Curie Insitut Teknologi Bandung Ecole doctorale chimie physique et analytique (ED 388) OXIDE AND COMPOSITE ELECTRON TRANSPORT LAYERS FOR EFFICIENT DYE-SENSITIZED SOLAR CELLS par Yuly KUSUMAWATI Thése de doctorat Prèsentee et soutenue publiquement le 10 Juin 2015 Devant un jury compose de: Dr. Thierry Pauportè Directeur de Recherche-CNRS Directeur de thèse Dr. M. A. Martoprawiro Professeur – ITB Co-directeur de these Prof. Fabrice Goubard Professeur Université Cergy-Pontoise Rapporteur Prof. Gilles Wallez Professeur – UPMC Examinateur Dr. Samir Farhat Maître de Conférérence – Université Examinateur Paris XIII Prof. Dr. Ir. Akhmad Herman Professeur – UI Rapporteur Yuwono, M.Phil.Eng Dr. Eng. Ferry Iskandar Professeur – ITB Examinateur Veinardi Suendo, Ph. D Professur - ITB Examinateur ACKNOWLEDGEMENT It would not have been possible to write this doctoral thesis without the help and support of the kind people around me to only some of them it is possible to give particular mention here. I would like to express the deepest appreciation to my supervisor in France, Dr. Thierry Pauporté, for his guidance and advice during finishing the research and writing publications in France, also for his patience to correct my thesis. I would also like to express my sincere gratitude to my supervisors in ITB Dr. M. A. Martoprawiro, Prof. Dr. Ing. Cynthia L. Radiman and Dr. Bambang Prijamboedi. Without them I cannot pass the tricky administration that let the student to graduate. There are no words to exprees my grateful to Prof. Dr. Ing. Cynthia L. Radiman’s patience. I would also like to thank Dr. Bambang Prijamboedi for the intense discussion and for correcting my draft. Dr. Samir Farhat and Prof. Noureddin Jouni from Laboratoire des Sciences des Procédés et des Matériaux, LSPM UPR 3407, Université Paris 13, Villetaneuse, France, are acknowledged for providing ZnO nanorod-like particles and Dr. Cèline Olivier from Institut des Sciences moléculaires, Université de Bordeaux, France is acknowledged for providing carbazole dye sensitizer. I would like to acknowledge Prof. Dr. Djulia Onggo, the head of doctoral school chemistry, ITB, for her time and her effort in manage the academic and administration requirement. I would also like to acknowledge Prof. Dr. Ir. Triyogi Yuwono, the rector ITS (Institut Teknologi Sepuluh Nopember), Prof. Dr. Perry Burhan (Dean of Mathematics and Natural Science Faculty, ITS) and Hamzah Fansury, Ph.D (Head of Chemistry Departement, ITS), who have gave me the permission to take a study. I would like to acknowledge the financial support from Campus France and the Higher Education Ministry of Indonesian (DIKTI) government in the framework of the DDIP collaboration program. I would also like to acknowledge Prof. Fida Madayanti Warganegara and Mrs. Tri for their effort to manage the program and DDIP’s students, including me. In addition, of course I would like to thank to all my friends in MPOE, Chimie- Paristech. Thank you Mongia for the dinner in your home, thank you Alexandra for keeping your finger crossed for me, thanks also to Jie, Ricardo, Xue, Frederic, Dora and Sana. Special ii thank to all my friends the DDIP scholarship holder and my friends in computational chemistry group ITB. Big thank is addressed to Atthar for helping the calculation and Hasan for keeping the HPC work well. The last, there are no words that can describe the support of my family, my husband, my mother, my father, my sisters and my daughter. iii ABSTRACT OXIDE AND COMPOSITE ELECTRON TRANSPORT LAYERS FOR EFFICIENT DYE-SENSITIZED SOLAR CELLS Dye-sensitized solar cell (DSSC) is built with combining many components in order to convert the solar energy to electricity. One of the DSSC components is a metal oxide semiconductor which plays the role of electron transport layer (ETL). It receives electrons from photoexcited dyes attached on its surface and ensures the electron transfer to the back contact of the solar cell. Developing the metal oxide that fulfills the requirements as an ETL is one of the effort to increase the DSSC power conversion efficiency. Three kinds of ETL have been developed and studied in this present work as a photoelectrode in DSSC. Those composed of (1) two kinds of TiO2-brookite nanoparticles, (TiO2_B1 and TiO2_B2), (2) the composite of anatase and graphene (TiO2_Gr) and (3) the nanorods like ZnO nanoparticles (ZnO_NR), respectively. All photoelectrode are prepared by doctor blading technique. The morphology of photoelectrodes have been characterized using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The layer thicknesses were measured using profilometry. For the film structural characterizations, a high-resolution X-ray diffractometer was used. The Fourier transform infrared (FTIR) and micro Raman measurement have been carried out to verify the TiO2_Gr composite preparation. The optical film properties (total transmission and total reflection) were recorded with a spectrophotometer equipped with an integrating sphere techniques. The cell performances were obtained by measuring the I-V curves of the cells undr calibrated illumination. To achieve an in-deep understanding of the cell functioning, the impedance spectroscopy (IS) technique has been studied over a large applied potential range. By doing IS study, the electronic structure, charge carrier lifetime (n), transport/collection time (tr) and electron transport parameters of the layers have been determined. The IS study of brookite-based photoelectrode has revealed that, compared to anatase, the brookite surface is less active for the recombination side reaction. A large charge transfer resistance, Rct, is shown which explains the high open circuit voltage of the brookite cells. However, the charge transport is much slower in the brookite phase due to a lower electrical conductivity. The computational study that has been performed, are in excellent agreement with the experimental results. iv The incorporation of 1.2 wt% of graphene into TiO2 photoelectrode led to an increase in conductivity by 60%. This increase induced a faster electron transport in photoelectrode. Moreover, the addition of graphene provoked the improvement in sensitized-layer sensitization and light absorbance. Both improvements resulted in a Jsc enlargement which is promising to apply in cobalt-based DSSCs. The composite of anatase and graphene, TiO2_Gr12 photoelectrode, that was sensitized by the Z907 and was coupled with 2+/3+ - - [Co(phen)3] , showed better cell performance compared to that the one coupled with I3 /I redox couple. This cell had performances comparable to the TiO2_A (as reference cell composed of pure anatase) photoelectrode that was sensitized using the Z907 and was coupled - - with I3 /I . The ZnO_NR showed good cell performances. D149 sensitized ZnO_NR cell - - coupled with I3 /I redox-couple had Power Conversion Efficiency (PCE) of 4.82%. The TG6 sensitized ZnO-NR cell showed the best ZnO-based DSSC performances and reached a PCE of 5.3%. We observed that, the outstanding properties of ZnO_NR lie in their large pores size that facilitates more dye to attach to their surface upon the sensitization process. Their advantages then become an interesting point to apply this photoelectrode in cobalt-based DSSC. The cobalt redox-couple species have bulky structures, they need large pores in order to transport through the photoelectrode. Our test employing carbazole dyes as the sensitizer revealed that the ZnO_NR photoelectrode has good performances with cobalt-based redox- couple compared to that triiodide/iodide one. The computational studies have been carried out to investigate the electronic properties of utilized dye sensitizers which are important to support the cell performances explanation. Briefly, all ETLs that have been developed in the present work have promising properties to be applied as photoelectrode in DSSC. The carefully study of their properties has revealed not only their advantages but also their limitation. This information will be beneficial as a consideration for the future work. Keywords: Dye-sensitized solar cell, electron transport layer, photoelectrode, TiO2, ZnO, graphene, impedance spectroscopy v Table of Contents ACKNOWLEDGEMENT .......................................................................................................... i ABSTRACT.............................................................................................................................. iv Table of Contents ..................................................................................................................... vii List of Figures ........................................................................................................................viiii List of Tables.......................................................................................................................... xiix List of Appendix......................................................................................................................xiii List of the Important Abbreviations and Symbols .................................................................... iv Chapter I: Introduction ............................................................................................................... 1 I.1. Background .......................................................................................................................... 1 I.1.1. Solar Energy as an Alternative of Renewable Energy.....................................................
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