Tong WU PhD defense

Glasses and Ceramics (V&C) team

Abstract
Kesterite Copper Zinc Tin Sulfide (CZTS) has emerged as a highly promising earth-abundant and environmentally benign material for thin-film solar cells. However, its development has been persistently constrained by a pronounced open-circuit voltage (VOC) deficit, primarily arising from the intricate interplay of bulk defects, interfacial recombination, and device architectural limitations.
This thesis presents a comprehensive, engineering strategy to address these challenges. Specifically, Germanium (Ge) doping is employed to passivate bulk cation defects; an oxygen-rich post- annealing treatment is introduced to suppress interfacial anion-related traps; and a cadmium-free Zinc Tin Nitride (ZnSnN2) buffer layer is developed to achieve optimal band alignment and environmentally sustainable device architecture. These approaches respectively led to remarkable performance advancements, achieving power conversion efficiencies of 12.25%, 11.51% (certified), and 10.0% for pure-sulfide CZTS solar cells. Collectively, this work demonstrates that an integrated approach combining bulk, interface, and device-level engineering is essential to overcome the intrinsic bottlenecks of CZTS technology, thereby advancing its potential toward efficient, sustainable, and commercially viable solar energy applications.

Jury
Maarja Grossberg-Kuusk Maarja, Professeure, Tallinn University of Technology / Reviewer
Judikael Le Rouzo, Professeur, Aix Marseille Université / Reviewer
Carmen Maria Ruiz Herrero, Chargée de Recherche, CNRS-Aix Marseille Université / Examiner
Shuo Chen, Professeur, University of Shenzhen / Examiner
Xianghua Zhang, Directeur de Recherche, CNRS-Université de Rennes, ISCR / PhD Supervisor
Guangxing Liang, Professeur, University of Shenzhen
/ PhD Co-Supervisor
Michel Cathelinaud, Ingénieur de Recherche, CNRS-Université de Rennes, ISCR / PhD Co-Supervisor

Contacts
Xianghua Zhang, xiang-hua.zhang@univ-rennes.fr
Michel Cathelinaud, michel.cathelinaud@univ-rennes.fr
Tong Wu, tong.wu@univ-rennes.fr