Quantum dot sensitized solar cells with efficiency over 12% based on tetraethyl orthosilicate additive in polysulfide electrolyte

Abstract

The undesired charge recombination loss, occurring at photoanode/electrolyte interfaces, as well as the high redox potential of the currently used polysulfide redox couple electrolyte restrain the photovoltaic performance, particularly the open-circuit potential (V_oc), of quantum dot sensitized solar cells (QDSCs). Herein, a valid and facile method to improve the performance of QDSCs is presented by modifying the polysulfide electrolyte with the addition of tetraethyl orthosilicate (TEOS). This approach is effective in a series of QDSC systems including the most commonly studied CdSe, CdSeTe, as well as Zn–Cu–In–Se (ZCISe) QDSCs. Experimental results indicate that with the use of 6 vol% TEOS additive in pristine polysulfide electrolyte at a staying time of 24 h, a remarkable enhancement in the conversion efficiency from 11.75% to 12.34% was obtained in ZCISe QDSCs. This photovoltaic performance is believed to be among the best result for all types of QD-based solar cells. The intrinsic mechanism for the performance improvement by the TEOS additive was verified by electrochemical impedance spectroscopy (EIS) and open-circuit voltage decay (OCVD) measurements.