基于提高染敏太阳能电池效率的上转换材料研究

Dye-sensitized solar cells (DSSC) have emerged as a promising candidate for development of the next generation solar cells owing to the potentially low cost and facile fabrication, and how to improve the light-to-electricity conversion efficiency is the key to the DSSC research field. Up-converting infrared photons into the visible light which can be readily absorbed by the dye, is one of the very effective and promising strategies. The state-of-the-art upconversion efficiency, however, is strongly limited by the narrow absorption band and low absorption strength. To address this limitation, novel approaches to enhancing the upconversion efficiency should be explored and developed urgently. In this research, firstly, rare earth ions Er3+/Yb3+ and hetero-ion M tri-doped nanocrystals NaYF4:Er3+,Yb3+,M (M = Li+, K+, Zn2+, Sr2+ and Bi3+) will be synthesized by a hydrothermal approach. Microstructure, morphology and upconversion properties will be characterized by XRD, Raman, SEM, TEM, photoluminescence, and etc. The influence of hetero-ions and their doping level on the upconversion spectra will be investigated in detail. Then, based on the result above, up-converting composites, i.e. QDs/NaYF4:Er3+,Yb3+,M, Ag/NaYF4:Er3+,Yb3+,M and Au/NaYF4:Er3+,Yb3+,M, will be prepared via the sensitization of quantum dots (QDs) and via surface plasmonic coupling of noble metal nanocrystals, respectively. The QDs, noble metal nanocrystals and their size dependence of the upconversion adsorption and emission will be examined systemically. And the mechanisms of enhancing upconversion efficiency will be discussed. Finally, the up-converting layers will be fabricated by the high efficient up-converting composites, and will be assembled in DSSC to improve the light-harvesting in the infrared region and thereby the photoenergy-conversion efficiency. The research findings, therefore, are of great significance to develop novel and highly efficient upconversion materials and to make full use of solar energy.

染敏太阳能电池（DSSC）具有成本低、制备简单等优点，有着广阔的应用前景。如何进一步提高其光电转换效率成为该研究领域的重要课题，利用上转换材料将红外光转换为染料可利用的可见光，是其中一种非常有效的途径。然而，现有的上转换材料吸光范围单一、上转换效率较低。为此，本项目以NaYF4为基质，先通过水热法合成三掺杂的Er3+/Yb3+/M（M为异质离子Li+、K+、Zn2+、Sr2+和Bi3+）上转换纳米晶；在此基础上，分别通过量子点敏化和贵金属纳米晶等离子体耦合，制备吸收范围较宽的、高效的上转换复合材料；利用红外、拉曼、X射线衍射和透射电镜等手段表征其结构、形貌和晶粒尺寸；系统研究异质离子的种类、掺杂量、量子点和贵金属纳米晶的尺寸等因素对上转换性能的影响，探讨上转换效率增强的机理；并将之应用于DSSC中，提高光电转换效率。因此，本项目的研究成果，对充分利用太阳能有着重要的意义。

染敏太阳能电池（DSSC）具有成本低、制备简单等优点，有着广阔的应用前景。如何进一步提高其光电转换效率成为该研究领域的重要课题，利用上转换材料将红外光转换为染料可利用的可见光，是其中一种非常有效的途径。然而，现有的上转换材料吸光范围单一、上转换效率较低。.本项目以NaYF4为基质，先通过水热法分别合成三掺杂的Er3+/Yb3+/M（M为异质离子Li+，Al3+，Bi3+，Ca2+和Mn2+）上转换纳米晶，不同异质离子对NaYF4:Er3+,Yb3+上转换发光性能、结构和形貌等因素的影响不同。而且，每一种掺杂离子均存在一合适的发掺杂浓度，此时其上转换发光强度最大；当掺杂10.0mol% Li+离子时，上转换红光和绿光强度分别提高了18.6倍和8.3倍，7.5 mol% Al3+离子其绿光和红光强度分别提高了10.1倍和9.8倍；4 mol%Bi3+离子使之绿光和红光强度分别提高了4.9倍和5.5倍；25mol% Ca2+离子掺杂使之绿光和红光强度提高了9.9倍和41.1倍；10mol% Mn2+离子掺杂使之绿光和红光强度提高了5.6倍和3.0倍。.在此基础上，分别通过量子点敏化和贵金属纳米晶等离子体耦合，制备吸收范围较宽的、高效的上转换复合材料。制备了三种不同尺寸的PbS量子点（平均粒径为4.1nm、7.8nm和12.9nm），制备了上转换复合材料PbS/NaYF4:Yb3+,Er3+,Ca2+，考察了量子点的用量及其尺寸对其上转换吸收谱和发射谱的影响，探讨了上转换效率增强的机理。研究结果表明，在980nm的光源激发下，量子点PbS对上转换发光影响不大；但在1550nm的光源激发下，上转换发光强度有所增加，而且量子点尺寸和用量对上转发光强度有着重要的影响，当量子点PbS的平均粒径为7.8nm，与上转换材料的摩尔比为5：1时，上转换发光强度最大，增大倍数为8.4倍，大大拓展了上转换材料NaYF4:Yb3+,Er3+在近红外区的吸收范围。.将上转换复合材料PdS/NaYF4:Er3+,Yb3+,Ca2+， Au/NaYF4:Er3+,Yb3+,Ca2+ 、Ag/NaYF4:Er3+,Yb3+,Ca2+制成了上转换层应用于DSSC中，大大提高了光电转换效率。因此，本项目的研究成果，对充分利用太阳能有着重要的意义。