A Biphase Tandem Redox Electrolyte for Efficient Quantum Dot-Sensitized Solar Cell

A new biphase tandem redox electrolyte system is designed by immobilizing imidazolium iodide on Co, N-doped carbon electrode in conjunction with polysulfide redox mediator in aqueous solution. Due to its biphasic feature, this redox system is enabled to separate the redox reactions in different phases, and hence, prevent the intertwined problem of redox reactions that occurred in one-phase tandem redox system. Investigations show that the biphase redox system can efficiently accelerate electron reduction, and thereby inhibit charge recombination. Consequently, quantum dot (QD)-sensitized solar cell fabricates using this biphase tandem redox together with CdSe QD-sensitized photoanode achieved a high cell efficiency of 6.85% at 100 mW cm2 simulated AM 1.5, showing about 33% increment as compared to the traditional pure polysulfide-based device (5.14%). The encouraging results indicate that the utilization of biphase tandem electrolytes can be an efficient way to improve the performance of sensitized solar cells. A new biphase tandem redox system is designed by confining the redox couples in different phases. While fabricated to CdSe quantum dots-sensitized solar cell, the overall conversion efficiency is improved from 5.3% for pure polysulfide electrolyte to 6.85% for tandem electrolyte, it is ascribed to its beneficial role of tandem electrolyte in inhibiting the charge recombination resulting from the accelerated electron reduction.image (c) 2023 WILEY-VCH GmbH