School of Materials Science and Engineering, Nanchang University, Nanchang 330031, China.
Xinyu Institute of New Energy, Xinyu University, Xinyu 338004, China.
Phys Chem Chem Phys. 2019 Dec 21;21(47):26133-26145. doi: 10.1039/c9cp04880d. Epub 2019 Nov 21.
In order to improve the power conversion efficiency (PCE) of quantum dot-sensitized solar cells (QDSC), a series of absorbent cotton derived carbon quantum dots (CQDs) with different dopants (namely carbamide, thiourea, and 1,3-diaminopropane) have been successfully synthesized by a one-pot hydrothermal method. The average particle sizes of the three doped CQDs are 1.7 nm, 5.6 nm, and 1.4 nm respectively, smaller than that of the undoped ones (24.2 nm). The morphological and structural characteristics of the four CQDs have been studied in detail. In addition, the three doped CQDs exhibit better optical properties compared with the undoped ones in the UV-vis and PL spectra. Then CQD-based QDSC are experimentally fabricated, showing that the short current density (J) and open circuit voltage (V) of the QDSC are distinctly improved owing to the dopants. Especially the QDSC with the 1,3-diaminopropane doped CQD achieves the highest PCE (0.527%), 299% larger than that without dopant (0.176%). In order to highlight a reasonable mechanism, the UV-vis diffuse reflectance spectrum of CQD sensitized TiO and the calculated energy band structures of various CQDs are investigated. It's found from the above analysis that the addition of carbamide, thiourea, and 1,3-diaminopropane is beneficial to obtain CQDs of smaller size, and with a smaller band gap and more nitrogenous or sulphureous functional groups, which enhance the light absorption performance and photo-excitation properties. The above factors are helpful to improve the J of QDSC. Nitrogen, acting as a donor to the CQDs, will assist the sensitized photoanode with a higher Fermi level, resulting in a larger V of the QSDC. Finally this study builds the relation among the microstructure of the CQDs, three characteristics of the CQDs (namely the spectra, energy band structure and functional groups) and the photoelectric properties of the QDSC, which will provide guidance for the modulation doping of CQDs to improve the PCE of QDSC.
为了提高量子点敏化太阳能电池 (QDSC) 的功率转换效率 (PCE)，我们通过一锅水热法成功合成了一系列具有不同掺杂剂（即尿素、硫脲和 1,3-二氨基丙烷）的吸附棉衍生碳量子点 (CQDs)。三种掺杂 CQDs 的平均粒径分别为 1.7nm、5.6nm 和 1.4nm，小于未掺杂的 CQDs（24.2nm）。详细研究了四种 CQDs 的形态和结构特征。此外，与未掺杂的 CQDs 相比，三种掺杂的 CQDs 在紫外-可见和 PL 光谱中表现出更好的光学性能。然后，我们通过实验制备了基于 CQD 的 QDSC，结果表明由于掺杂剂的存在，QDSC 的短路电流密度 (J) 和开路电压 (V) 得到了明显提高。特别是用 1,3-二氨基丙烷掺杂 CQD 的 QDSC 获得了最高的 PCE（0.527%），比未掺杂的 PCE（0.176%）提高了 299%。为了突出合理的机制，我们研究了 CQD 敏化 TiO 的紫外-可见漫反射光谱和各种 CQDs 的计算能带结构。从上述分析可知，添加尿素、硫脲和 1,3-二氨基丙烷有利于获得尺寸更小、带隙更小且含有更多氮或硫官能团的 CQDs，从而增强了光吸收性能和光激发性能。这些因素有助于提高 QDSC 的 J。氮作为 CQDs 的供体，将帮助敏化光阳极具有更高的费米能级，从而使 QSDC 的 V 更大。最后，本研究建立了 CQDs 的微观结构、CQDs 的三个特性（即光谱、能带结构和官能团）以及 QDSC 的光电性能之间的关系，为 CQDs 的调制掺杂以提高 QDSC 的 PCE 提供了指导。
