【作者】 张莉；

【导师】 杨德仁； 皮孝东；

【作者基本信息】 浙江大学 ， 材料科学与工程， 2012， 硕士

【摘要】 与体硅材料相比,硅纳米晶体具有量子限域效应和多激子等效应,因而具备独特的电、光学特性,给太阳电池的发展注入了新的活力。硅纳米晶体能够以多种方式应用于太阳电池中：其一,利用硅纳米晶体制作新型太阳电池,比如多激子太阳电池、中间态太阳电池和热载流子太阳电池等；其二,将硅纳米晶体与传统太阳电池相结合,通过减反射和下转换等作用提高太阳电池效率；此外,硅纳米晶体也可与有机物或无机物相结合,制备具有复合结构的太阳电池。但硅纳米晶体的稳定性不好,易被氧化,难均匀分散在常规溶剂中,这两个因素制约了硅纳米晶体的广泛应用。本文的工作,集中解决如何通过表面改性抑制硅纳米晶体的氧化,改善它在溶剂中的分散性,最终,将经过表面改性的硅纳米晶体用于提高传统晶体硅太阳电池的效率。首先,利用等离子体硅纳米晶体合成系统制备硅纳米晶体。通过改变气体流量、等离子体气压等参数调节硅纳米晶体的尺寸,最终实现硅纳米晶体的光致发光峰位可调。随后,利用苯乙烯、十二烯和十八烯对硅纳米晶体进行表面改性。我们发现碳链越短,改性越容易进行,有机基团在硅纳米晶体表面覆盖率越高,改性后的硅纳米晶体的荧光量子效率越高。当改性时间过长,链接在硅纳米晶体表面的有机基团因空间位阻发生结构重排,在硅纳米晶体表面引入非辐射复合中心,导致硅纳米晶体的量子效率下降。氢化硅烷化反应只可抑制,但不能完全避免硅纳米晶体被氧化。将改性后的硅纳米晶体存放在空气中,硅纳米晶体仍会被缓慢氧化；氧化后硅纳米晶体的发光峰位发生蓝移,而荧光量子效率会受到悬挂键被钝化和取代基团之间相互作用导致结构畸变这两个因素的影响,表现出先升高后降低的变化趋势。最后,分别利用苯乙烯和十八烯改性的硅纳米晶体配制硅墨水。通过喷墨打印的方式,将硅墨水有效沉积在太阳电池表面,形成具有多孔结构的硅纳米晶体薄膜。印刷硅墨水后,太阳电池在短波段(300-400 nm)和长波段(640-1100nm)的反射率降低(光吸收增强)。而太阳电池的外量子效率则受到硅纳米晶体薄膜的减反射、硅纳米晶体对短波长光的吸收和下转换等因素的影响,在短波和长波段有不同程度的提高。对于用苯乙烯改性的硅纳米晶体配制的硅墨水,太阳电池效率的相对提高值最高达到1.54%(电池效率从17.10%上升到17.36%)。对于用十八烯改性的硅纳米晶体配制的硅墨水,太阳电池效率的相对提高值最高达2.02%(电池效率从17.19%上升到17.53%)。更多还原

【Abstract】 Silicon nanocrystals (Si NCs) exhibit fascinating electronic and optical properties. Si NCs are now intensively studied for photovoltaic application. They can be used to fabricate novel solar cell (multiple-exciton solar cells, intermediate-band solar cells, and hot-carrier solar cells), or incorporated in conventional solar cells. It has been realized that during the processing of Si NCs surface modification must be carried out to render the dispersibility of Si NCs in desired media and retard the oxidation of Si NCs.Freestanding Si NCs with different sizes are synthesized in a plasma system. Efficient photoluminescence (PL) from Si NCs in the visible and near-infrared spectral regions has been obtained.The surface of as-synthesized hydrogen-passivated Si NCs is modified via a hydrosilylation scheme with styrene. dodecene and octadecene. It is found that the peak position of the PL from hydrosilylated Si NCs is hardly affected by the modifier or the hydrosilylation time, but the modification time. However, the quantum yield (QY) of the PL from hydosilylated Si NCs decreases with the increase of hydrosilylation time for all the samples with different modifier. During the storage of hydrosilylated Si NCs in air the PL from hydrosilylated Si NCs blueshifts, while the PL QY for hydosilylated Si NCs initially increases and then decreases. The underlying mechanisms for all the optical behavior of hydrosilylated Si NCs are discussed.Hydosilylated Si NCs are dispersed in solvents to form Si ink. Si-NC films are obtained at the surface of Si solar cells by means of ink-jet printing. The reflectance and the external quantum efficiency (EQE) of Si solar cell have been measured. Enhancement of solar cell efficiency up to 2.02% is observed. Both the antireflection of Si-NC films and the downshifting of Si NCs contribute to the efficiency enhancement.更多还原