Increased Quantum Dot Loading by pH Control Reduces Interfacial Recombination in Quantum-Dot-Sensitized Solar Cells

Abstract

The power conversion efficiency of quantum-dot-sensitized solar cells (QDSSCs) hinges on interfacial charge transfer. Increasing quantum dot (QD) loading on the TiO2 anode has been proposed as a means to block recombination of electrons in the TiO2 to the hole transport material; however, it is not known whether a corresponding increase in QD-mediated recombination processes might lead to an overall higher rate of recombination. In this work, a 3-fold increase in PbS QD loading was achieved by the addition of an aqueous base to negatively charge the TiO2 surface during Pb cation deposition. Increased QD loading improved QDSSC device efficiencies through both increased light absorption and an overall reduction in recombination. Unexpectedly, we also found increased QD size had the detrimental effect of increasing recombination. Kinetic modeling of the effect of QD size on interfacial charge transfer processes provided qualitative agreement with the observed variation in recombination lifetimes. These results demonstrate a robust method of improving QD loading, identify the specific mechanisms by which increased QD deposition impacts device performance, and provide a framework for future efforts optimizing the device architecture of QDSSCs.

Quantum dot sensitized solar cell: Recent advances and future perspectives in photoanode

“…Roelofs et al [138] have observed three fold of PbS quantum dot loading on TiO 2 with varying pH of cation solution. Because of dense QD deposition, enhanced efficiency is achieved.…”

Effect of sodium acetate additive in successive ionic layer adsorption and reaction on the performance of CdS quantum-dot-sensitized solar cells

“…Various semiconductors or versatile QD combinations, such as CdS [9e11], CdSe [12e14], PbS [15,16], CuInS 2 [17,18], CdSe/CdTe [19] and CdS/CdSe [20,21] had been adopted as the sensitizers of QDSSCs. In order to obtain highly efficient QDSSCs, at least three important issues must be taken into consideration: (1) the QD sensitizer with narrow band gap and suitable band alignment, (2) the redox couple [22,23] able to scavenge photoexcited holes [24] and non-corrosive to QD sensitizers, and (3) the counter electrode [25,26] possessing highly electrocatalytic activity and good stability.…”

Impact of Conformality and Crystallinity for Ultrathin 4 nm Compact TiO2 Layers in Perovskite Solar Cells

“…The spray‐pyrolysis precursor solution was titanium diisopropoxide bis(acetylacetonate) in ethanol. The exact deposition parameters used are taken from those in literature and our previous work on DSSCs and QDSSCs, and are detailed in the experimental section. A manual spray‐pyrolysis process was used, which aerosolizes the precursor solution.…”