通过S2-中间态将CdSe量子点有机配体转化为ZnS保护层及其器件光伏特性

通过S2-中间态将有机配体三辛基氧膦(TOPO)转化为ZnS保护层,显著改善了CdSe量子点(QDs)器件的转换效率.配体交换后的傅里叶变换红外(FTIR)光谱结果表明,有机配体已被S2-离子配体取代;离子反应后的X射线光电子能谱(XPS)结果表明S2-离子配体反应生成了ZnS,紫外-可见(UV-Vis)吸收光谱结果表明量子点溶液吸收峰位没有发生明显改变,透射电子显微镜(TEM)结果表明配体交换后量子点粒径减小.电化学阻抗谱(EIS)结果表明光照条件下有机配体转化为ZnS保护层后TiO2/QDs/电解质界面电阻减少,证明该条件下正向电子传输增强;强度调制光电压谱(IMVS)和强度调制光电流谱(IMPS)结果表明电子寿命和扩散速度增加.相比于有机配体,形成ZnS保护层后的量子点敏化太阳能电池(QDSC)效率由0.98%提高到1.75%,相对提高了1.78倍.

Transforming Organic Ligands into a ZnS Protective Layer through the S2- Intermediate State in ex situ CdSe Quantum Dot Devices

In this paper, the tri-n-octylphosphine oxide (TOPO) ligand on CdSe quantum dots (QDs) are changed to ZnS coating layer through S^2- intermediate state. After ligand exchange, the Fourier transform infrared (FTIR) spectra indicate that the long chain organic ligands are replaced by S^2- ions. After ionic reaction, the generation of ZnS is confirmed by X-ray photoelectron spectroscopy (XPS) measurements. In addition the UV-Vis absorption peaks did not move and transmission electron microscopy (TEM) results show that the diameters of the quantum dots decrease. Electrochemical impedance spectroscopy (EIS) results show that the interface resistance between the TiO₂/QDs/electrolyte is reduced under illumination conditions, meaning that forward electron transport was enhanced. In addition, the intensity-modulated photovoltage spectroscopy (IMVS) and intensity-modulated photocurrent spectroscopy (IMPS) results reveal an increase in the electronic lifetime and diffusion rate increased. Finally, the conversion efficiency increases by 1.78 times from 0.98% (TOPO ligand) to 1.75% (ZnS coating).