宽带染料敏化红外上转换核壳纳米晶的制备及性能研究

A major problem limiting the conversion efficiency of photovoltaic (PV) cells is their insensitivity to broadband absorption of full solar spectrum. Upconversion luminescent materials are capable of converting infrared light into a particular wavelength photons absorped by PV cells. Specailly, organic infrared dye can be used as an antenna for broadband absorption of full solar spectrum in which the upconversion occurshave been used to minimize the losses in the solar-cell-based energy conversion process. That is a promising way to overcome the Shockley–Queisser efficiency limit of a single-junction solar cell. However, research on improving conversion efficiency of PV cells based on the upconversion materials and infrared dye has been rarely reported. Here, we propose and demonstrate the viability of a new strategy.to design and preprare upconversion core-shell nanocrystals, in which different activators are separately incorporated into the core and shell.layer of a nanoparticle. And then multi-bands of infrared absorption can be obtianed. More importantly, organic infrared dyes are crosslinked to surface of nanoparticles via covalent conjugation strategy. That composite can enhance the infrared absorption of lanthanide nanoparticles.based on increased and spectrally infrared broadened absorption, using organic infrared dyes as sensitizers. Therefore, the practical applicability of the most efficient known upconversion materials and broadband absorption dye at moderate light intensities can make up their extremely weak and narrowband infrared absorption of rare-earth ions doped materals. We can evaluate the application prospect of the composite in PV cells field by optical performance and efficiency test.

硅基材料不能对全波段太阳发射光谱进行宽带吸收是限制硅基太阳能电池效率提升的瓶颈。上转换材料能有效拓展硅基材料对硅带隙以下特定波段太阳光的吸收，而有机染料能宽带吸收红外波段太阳光来敏化上转换材料红外吸收，这是突破硅基太阳能电池理论效率极限的理想方法。然而目前缺乏将两者有机结合进行宽带吸收红外波段太阳光，敏化上转换材料红外吸收来提高硅基太阳能电池效率的研究。本项目拟设计和制备核壳结构的氟化物纳米晶，利用晶核与壳层将稀土发光离子在空间上进行隔离，实现硅带隙以下多波段红外吸收。尤其将有机染料引入到上转换体系，通过键联的方式将有机染料固化在纳米晶表面，该复合材料具有宽带吸收硅带隙以下波段太阳光的性质，并将吸收的红外波段太阳光转化成硅基材料可吸收的光，将弥补稀土离子窄带吸收红外波段太阳光增加太阳能电池效率的不足，更全面地利用太阳能光谱。并通过光学性能以及效率测试综合评估其在硅基太阳能电池中的应用前景。

太阳能电池材料不能对全波段太阳发射光谱进行宽带吸收是限制电池效率提升的瓶颈 。上转换材料能有效拓展带隙以下特定波段太阳光的吸收，而有机染料能宽带吸收红外波段太阳光来敏化上转换材料在红外区的吸收，这是突破太阳能电池理论效率极限的理想方法。本项目主要围绕着上转换核壳结构设计及宽带染料敏化的上转换纳米材料提高太阳能电池效率开展研究，我们先对上转换过程进行研究，首先，通过对不同基质（如：NaYF4，NaGdF4，YF3和小尺寸的CaF2）的对比，发现NaYF4核壳结构的上转换效率最高，接下来着重研究了Er3+荧光特性。随后提出采用宽带近红外染料敏化的上转换材料解决对现有太阳能电池无法吸收近红外太阳光的问题方案，使用可以宽带吸收670-860nm波段近红外太阳光的IR783染料，能够成功的将近红外光转换到太阳能电池可以利用的可见光范围。应用该种设计的材料可以将染料敏化太阳能电池的光电转换效率从7.573%提升到8.568%，使其光电转换效率提升初始值的13.1%，其中上转换过程贡献7.1%，散射作用贡献6.0%。综上所述，我们已经对于本基金提出的问题进行了系统的研究，并得出了超过预期期待的结果和一些更深层次的结果，可以说我们顺利完成了本自然科学基金项目。