Sensitized Solar Cells Based on Ternary Metal Oxide Nanowires and a Physical Approach for Quantum Dot Deposition

W. Wang
University of Wyoming, US

Keywords: nanowires, quantum dots, sensitized solar cells

Summary:

In this work we discuss sensitized solar cells (SSCs) based on ternary metal oxide nanowires such as Zn2SnO4 nanowires. Optimized conditions for a reproducible synthesis of Zn2SnO4 nanowires are achieved, and a more than 0.1 V improvement on open-circuit voltage has been observed when Zn2SnO4 nanowires are used as the photoanode instead of Zn2SnO4 nanoparticles. The higher open-circuit voltage could be attributed to a suppressed back electron transfer process in the devices. We also present a physical deposition-based, one-step quantum dot (QD) synthesis and assembly on nanowires for QD-SSC applications. Typical solution-based synthesis of colloidal QDs involve toxic wet chemicals and nontrivial ligand exchange processing, and the effects of the ligands on carrier transport have not been fully understood. Using pulsed laser deposition, CdSe QDs are successfully coated on Zn2SnO4 nanowires without ligand molecules, and the coverage can be controlled by adjusting the laser fluence. Growth of QDs in dense nanowire network structures has also been achieved, and QD-SSCs fabricated using this method exhibited promising device performance. This approach can be further applied for the assembly of QDs where ligand exchange is difficult, such as the PbS QDs, and could possibly lead to reduced fabrication cost and improved device performance.