Abstract
Sensitized NiO based photocathode is a new field of investigation with increasing scientific interest in relation with the development of tandem dye-sensitized solar cells (photovoltaic) and dye-sensitized photoelectrosynthetic cells (solar fuel). We demonstrate herein that PbS quantum dots (QDs) represent promising inorganic sensitizers for NiO-based quantum dot-sensitized solar cells (QDSSCs). The solar cell sensitized with PbS quantum dot exhibits significantly higher photoconversion efficiency than solar cells sensitized with a classical and efficient molecular sensitizer (P1 dye = 4-(Bis-{4-[5-(2,2-dicyano-vinyl)-thiophene-2-yl]-phenyl}-amino)-benzoic acid). Furthermore, the system features an IPCE (Incident Photon-to-Current Efficiency) spectrum that spreads into the infra-red region, reaching operating wavelengths of 950 nm. The QDSSC photoelectrochemical device works with the complexes tris(4,4′-ditert-butyl-2,2′-bipyridine)cobalt(III/II) redox mediators, underscoring the formation of a long-lived charge-separated state. The electrochemical impedance spectrocopy measurements are consistent with a high packing of the QDs upon the NiO surface, the high density of which limits the access of the electrolyte and results in favorable light absorption cross-sections and a significant hole lifetime. These notable results highlight the potential of NiO-based photocathodes sensitized with quantum dots for accessing and exploiting the low-energy part of the solar spectrum in photovoltaic and photocatalysis applications.
Highlights
We find that the system delivers up to 5.27 mA/cm[2] of short-circuit current density with an IPCE extending well into the IR range exceeding 950 nm–results that highlight the compelling potential of p-QDSSCs
It has been clearly demonstrated that the passivation of the traps in quantum dots (QDs) is a crucial factor for highly performing solar cells[4,5]
To maximize the hole-injection efficiency, the PbS capped with oleic acid were treated with a solution of tetrabutylammonium iodide (TBAI)
Summary
The relative position of the valence and conduction band potentials of the overlaid CdS/CdSe QDs decreases the charge recombination reactions of the injected hole with the electron in the QD or with the electrolyte, reducing the major losses associated with undesirable pathways. NiO films sensitized with CdSe quantum dots have been successfully implemented in photoelectrocatalytic solar cells for hydrogen production[17,28,29,30]. These aforementioned attractions and properties of QDs have prompted our efforts to assess the possibility of using a low bandgap QD, such as PbS, to prepare efficient NiO-based photoelectrochemical devices. We find that the system delivers up to 5.27 mA/cm[2] of short-circuit current density with an IPCE extending well into the IR range exceeding 950 nm–results that highlight the compelling potential of p-QDSSCs
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