A novel polysulfide hydrogel electrolyte based on low molecular mass organogelator for quasi-solid-state quantum dot-sensitized solar cells

Abstract

A quasi-solid-state quantum dot-sensitized solar cell (QDSSC) is fabricated by using 12-hydroxystearic acid as a low molecular mass organogelator to gelate the polysulfide electrolyte. Noticeably, the gel to liquid transition temperature of this polysulfide hydrogel electrolyte is 96 °C, which contributes to the long-term stability of the quasi-solid-state QDSSC (QS-QDSSC). The influences of gelation on the charge transport, electron recombination and photovoltaic performance of the QS-QDSSC are investigated by electrochemical impedance spectroscopy. Moreover, the network of the hydrogel is investigated by the Field emission scanning electron microscopy and polarized optical light microscopy. It is found that the charge transport is influenced by the network in the hydrogel electrolyte, and the accelerated electron recombination at the photoanode/electrolyte interface leads to the decreased open-circuit voltage. The QS-QDSSC exhibits an energy conversion efficiency of 2.40% at AM 1.5 (100 mW cm−2) which is slightly lower than that of liquid electrolyte based cell (2.88%). However, the QS-QDSSC exhibits significantly improved stability during the accelerated thermal test. Especially, during the accelerated aging test, the short-circuit current density (Jsc) of the liquid electrolyte based QDSSC sharply decreased to nearly 35% of its initial value, while there is relatively less change in the Jsc for the QS-QDSSC.