Hole transport materials mediating hole transfer for high efficiency quantum dot sensitized solar cells

Abstract

The slow hole transfer from quantum dots (QDs) to the polysulfide redox couple electrolyte deteriorates the photovoltaic performance of QD-sensitized solar cells (QDSCs). To accelerate hole transfer and improve the performance of QDSCs, a series of hole transport materials (HTMs, including graphene oxide (GO), diphenyl sulfide (DPS), and 2,2′,7,7-tetrakis[N,N-di(4-methoxyphenyl)-amino]-9,9′-spiro-bifluorene (Spiro)) are deposited on the QD-sensitized photoanode and serve as hole transfer interplay media. The experimental results indicate that except for Spiro, the other two HTMs have a positive effect on improving the photovoltaic performance of the resulting cell device. The intrinsic mechanism of the effect of GO on the performance of the corresponding cell device is studied systematically. Photoluminescence decay measurements indicate clearly that the introduction of GO on the interface between QDs and the electrolyte can accelerate the hole transfer dynamics by about 4.7-fold. GO modification on the QD-sensitized photoanode can improve the power conversion efficiency (PCE) of ZCISe QDSCs from the original 12.50% to 13.84%, which is among the best performances for QDSCs.