Fabrication of Shape-Controlled Inorganic Nanomaterials for Enhanced Light Absorption in Solar Cells

Abstract

Photovoltaic (PV) devices can effectively convert sunlight into clean electrical power and provide a virtually unlimited supply of usable energy that is sustainable and environmentally benign in operation. Nanomaterials open up new possibilities to achieve higher solar energy conversion efficiencies at lower fabrication costs, as they allow the use of inexpensive materials and processing technologies to harvest sunlight by efficiently capturing photon energy over a broad spectral range, and then quickly separating and collecting photo-generated charge carriers. However, the bandgap energy of the semiconductors places a fundamental upper limit on solar energy conversion efficiency for solar cells, known as Shockley-Queisser limit which restricts the efficiency to a maximum of about 31% for unconcentrated sunlight irradiation, using a semiconductor material with an optimized band-gap of around 1.35 eV. This dissertation describes the fabrication of shape-controlled inorganic nanomaterials for effective light harvesting in solar cells. CeO2:Eu3+ nano-octahedra were prepared using a simple hydrothermal method and introduced to the TiO2 layer of the photoanode in a dye-sensitized solar cell (DSSC) device. The as-synthesized CeO2:Eu3+ nano-octahedra possess the dual functionality of light scattering and downconversion luminescent properties, leading to increased photocurrent in DSSCs. NaYF4:Yb3+, Er3+ hexagonal nanoprisms were fabricated via a simple hydrothermal process. NaYF4:Yb3+, Er3+ hexagonal nanoprisms were introduced to the TiO2 mesoporous layer in a perovskite solar cell (PSC) device as upconverting centers. Size-controlled Ag@SiO2 nanoplates were synthesized by seed-mediated growth method and sol-gel reaction. After introduction of Ag@SiO2 nanoplates in PSC, photocurrent was considerably increased by localized surface plasmon resonance (LSPR) effect of Ag@SiO2 nanoplates. The nanomaterials presented in this dissertation could be applied to various photovoltaic fields such as DSSC, PSC, and organic photovoltaic (OPV). In addition, this dissertation might not only provide a facile synthetic route for shape-controlled inorganic nanomaterials but also offer an understanding of efficient light harvesting for high-performance PV devices.