Poly(vinyl pyrrolidone): a superior and general additive in polysulfide electrolytes for high efficiency quantum dot sensitized solar cells

Charge recombination losses are primarily responsible for the modest photovoltaic performance of quantum dot sensitized solar cells (QDSCs). Charge recombination occurring at the photoanode/electrolyte interface contributes significant energy loss in QDSC devices. Herein, a facile method to reduce the recombination loss by modifying the polysulfide electrolyte with the addition of poly(vinyl pyrrolidone) (PVP) as an efficient and general additive was introduced. It was found that the PVP modified polysulfide electrolyte could significantly improve the photovoltaic performance of QDSCs, especially the open-circuit voltage and fill factor. In addition, the PVP modified electrolyte is widely applicable to various QD sensitizer based systems. Impedance spectroscopy and open circuit voltage decay (OCVD) measurements reveal that the charge recombination processes occurring at the TiO2/QDs/electrolyte interfaces were remarkably inhibited using the PVP modified electrolyte. The average power conversion efficiency (PCE) was improved remarkably by 9% and a champion PCE of 9.77% was obtained with 20 wt% PVP in the polysulfide electrolyte for CdSexTe1-x based QDSCs. Moreover, the stability of the constructed QDSCs was also improved by employing the PVP modified polysulfide electrolyte.