Sun Yu, Jiang Guocan, Zhou Mengsi, Pan Zhenxiao, Zhong Xinhua
School of Chemistry and Molecular Engineering, East China University of Science and Technology Shanghai 200237 China
College of Materials and Energy, South China Agricultural University 483 Wushan Road Guangzhou 510642 China
RSC Adv. 2018 Aug 24;8(52):29958-29966. doi: 10.1039/c8ra05794j. eCollection 2018 Aug 20.
It has been well established that polymer additives in electrolyte can impede the charge recombination processes at the photoanode/electrolyte interface, and improve performance, especially , of the resulting sensitized solar cells. However, there are few reports about the effect of electrolyte additives on counter electrode (CE) performance. Herein, we systematically investigated the effect of polyethylene glycol (PEG) additives with various molecular weights ( from 300 to 20 000) in polysulfide electrolyte on the performance of two representative CdSe and Zn-Cu-In-Se (ZCISe) quantum dot sensitized solar cells (QDSCs), and explored the mechanism of the observed effects. Electrochemical impedance spectroscopy measurements indicate that all PEG additives can improve the charge recombination resistance at the photoanode/electrolyte interface, therefore suppressing the unwanted charge recombination process, and enhancing the of the resulting cell devices accordingly. On the CE side, with the increase of of PEG additives, the initial effect of reducing the charge transfer resistance at the CE/electrolyte interface evolves into an increasing resistance; accordingly the initial positive effect on FF turns into negative one. Accordingly, low PEG can improve efficiency for both CdSe (increasing from 6.81% to 7.60%) and ZCISe QDSCs (increasing from 9.26% to 10.20%). High PEG is still effective for CdSe QDSCs with an efficiency of 7.38%, but falls flat on ZCISe QDSCs (with an efficiency of 9.11%).
电解质中的聚合物添加剂能够阻碍光阳极/电解质界面处的电荷复合过程，并提高由此制备的敏化太阳能电池的性能，这一点已经得到了充分证实。然而，关于电解质添加剂对反电极（CE）性能影响的报道却很少。在此，我们系统地研究了聚乙二醇（PEG）添加剂（分子量从300到20000）在多硫化物电解质中对两种代表性的CdSe和Zn-Cu-In-Se（ZCISe）量子点敏化太阳能电池（QDSCs）性能的影响，并探讨了观察到的效应的机制。电化学阻抗谱测量表明，所有PEG添加剂都能提高光阳极/电解质界面处的电荷复合电阻，从而抑制不必要的电荷复合过程，并相应提高所制备电池器件的性能。在CE方面，随着PEG添加剂分子量的增加，其降低CE/电解质界面处电荷转移电阻的初始效应演变为电阻增加；相应地，对填充因子（FF）的初始正向效应变为负向效应。因此，低分子量的PEG可以提高CdSe（从6.81%提高到7.60%）和ZCISe QDSCs（从9.26%提高到10.20%）的效率。高分子量的PEG对效率为7.38%的CdSe QDSCs仍然有效，但对ZCISe QDSCs却效果不佳（效率为9.11%）。
