Ultra-thin oxide shell silver nano triangle can effectively enhance the photoelectricity of solar cells
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The surface plasmon resonance effect of metal nanoparticles is considered to be an effective means to increase the light absorption of solar cells. However, when metal nanoparticles are added to the active layer of an organic solar cell, the metal nanoparticles can accept both electrons and voids. Holes, which lead to recombination of electrons and holes, seriously affect the photoelectric conversion efficiency of the device.
Recently, the team of Sun Jicheng of the Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, used the sol-gel method to synthesize an Ag@3 oxide (SiO2 or TiO2) nanotriangle with an ultrathin shell using the silver nanotriangle as a model. Oxide shell thickness can be controlled continuously adjustable from 2-15nm. The oxide shell can effectively avoid the recombination of electrons and holes, and the ultrathin shell does not affect the surface plasmon resonance effect of the Ag nanotriangle. Related results have been published on Small.
When the Ag nano-triangle is added to the photovoltaic device, it will bring several effects, such as enhancing light scattering, reducing the internal resistance of the device, enhancing the surface plasmon resonance enhancement effect, and increasing the recombination probability of electrons and holes. The first three of them will bring positive enhancement results to the photoelectric conversion efficiency of the device, but the recombination of electrons and holes will reduce the photoelectric conversion efficiency of the device, so it is necessary to suppress this factor.
On the other hand, the surface-plasmon-enhancing effect of metal nanoparticles is usually attenuated in an exponential manner, so its range of action is limited to a very small range (less than 20 nm). Therefore, the thickness of the shell has a great influence on the utilization of the surface plasmon resonance effect of the metal nanoparticles. The team used a sol-gel method to synthesize an ultra-thin (~2nm) oxide shell that can both enhance the stability of the silver nanotriangle and suppress the accumulation of electrons or holes on the metal surface.
Absorption and steady state fluorescence spectroscopy studies have shown that the introduction of silver nanoshells not only enhances the light absorption of the active layer but also promotes the separation of photogenerated charges. Transient absorption spectroscopy studies have shown that the addition of silver nanostructures, light-induced absorption was significantly enhanced, indicating that the concentration of photoexcited exciton increased. This proves that the surface plasmon resonance effect of silver nanoparticles plays a significant role in promoting light absorption. The corresponding photovoltaic device research shows that its photoelectric conversion efficiency can be increased by 30%. Thus, it is proved that the ultra-thin shell metal nanoparticles can fully utilize the surface plasmon resonance effect of the metal nanoparticles. This provides new ideas and lessons for the design of other types of solar energy conversion devices.
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