Optimization of TiO2 for Low-Temperature Dopant-Free Crystalline Silicon Solar Cells
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This study explores the deposition and post-deposition treatment of TiO2 films in the context of using those films as electron selecting layers in diffusion-free solar cells. The passivation provided by TiO2 films is known to improve after annealing. Therefore, the effect of annealing on electrical performance of the films is analyzed in this study. The study reveals that annealing may lead to a formation of thin interfacial silicon oxide which may impede the transport of electrons to the desired contact. It is also noted that annealing does not contribute significantly to lowering of reverse saturation current, and the ideality factor values also remain the same. Interestingly, while annealing improves the lifetime, the same is not reflected in electrical behavior of diodes. A plausible explanation of this behavior is given on the basis of numerical modeling of the fabricated device. Finally using the as-deposited TiO2 film as electron collecting contact and MoO3 as a hole quencher, solar cells are fabricated with an efficiency of 5.52%.
KeywordsTiO2 Passivation Heterojunction solar cell Carrier selective contacts Electron transport layer
We thank Prof. Saurabh Lodha for giving access to atomic layer deposition. The authors gratefully acknowledge the support of Ministry of New and Renewable Energy (MNRE), Solar Energy Research Institute for India and the United States (SERIIUS), National Centre for Photovoltaic Research and Education (NCPRE) and Centre of Excellence in Nanoelectronics (CEN).
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