Efficient quantum-dot-sensitized solar cells with improved stability using thixotropic polymer/nanoparticles-based gel electrolyte

In this article, the preparation of a gel electrolyte that consists of a polysulfide electrolyte with xanthan gum (XG) thixotropic gel and TiO2 nanoparticles (NPs) is reported for the development of improved performance of quantum-dot-sensitized solar cells (QDSSCs). Natural polysaccharide XG exhibited thixotropic sol-gel transitions, by which it can reversibly be converted from sols to high-viscosity gels under shear stress. XG is, for the first time, used to passivate the surface trap states or act as steric hindrance between TiO2/QDs/electrolyte interfaces. The incorporation of TiO2 NPs in the XG gel electrolyte improved the ionic conductivity of the gel electrolyte. For the Cu-In-Se QDSSC with gel electrolytes, the conversion efficiencies were 7.25% and 8.19% for XG and XG/NP gel electrolytes, respectively, whereas, the liquid electrolytes only delivered an efficiency of 6.86% under simulated sunlight (AM 1.5, 100 mW cm(-2)). Moreover, electrochemical analysis revealed that enhanced charge transfer and suppressed electron-hole recombination process occurred more frequently at the TiO2/QDs/electrolyte in QDSSCs with the XG/NP gel electrolyte compared with those with the liquid and XG gel electrolyte. Most importantly, the XG/NP gel electrolyte is also effective in various I-III-VI-based QDSSCs, including Cu-In-S and Ag-In-Se QDSSCs, for improving the cell power conversion efficiencies and stability because of the synergistic effect of XG and TiO2 NPs in polysulfide electrolytes. Notably, the best cell devices (Cu-In-S QDSSCs) constructed using XG/NP gel electrolytes have long-term stability under one-sun illumi- nation, retaining 90% of the initial device's efficiency after 150 h. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study reported the preparation of a gel electrolyte using XG and TiO2 NPs to improve the performance of QDSSCs, achieving higher photoconversion efficiencies and stability. XG exhibited thixotropic sol-gel transitions, and the incorporation of TiO2 NPs improved the ionic conductivity of the gel electrolyte, passivating surface trap states or acting as steric hindrance.