CdSe Quantum-Dot-Sensitized Solar Cell with ∼100% Internal Quantum Efficiency

Abstract

We have constructed and studied photoelectrochemical solar cells (PECs) consisting of a photoanode prepared by direct deposition of independently synthesized CdSe nanocrystal quantum dots (NQDs) onto a nanocrystalline TiO(2) film (NQD/TiO(2)), aqueous Na(2)S or Li(2)S electrolyte, and a Pt counter electrode. We show that light harvesting efficiency (LHE) of the NQD/TiO(2) photoanode is significantly enhanced when the NQD surface passivation is changed from tri-n-octylphosphine oxide (TOPO) to 4-butylamine (BA). In the PEC the use of NQDs with a shorter passivating ligand, BA, leads to a significant enhancement in both the electron injection efficiency at the NQD/TiO(2) interface and charge collection efficiency at the NQD/electrolyte interface, with the latter attributed mostly to a more efficient diffusion of the electrolyte through the pores of the photoanode. We show that by utilizing BA-capped NQDs and aqueous Li(2)S as an electrolyte, it is possible to achieve ∼100% internal quantum efficiency of photon-to-electron conversion, matching the performance of dye-sensitized solar cells.

An integrated approach to realizing high-performance liquid-junction quantum dot sensitized solar cells

“…37). This approach has been utilized to realize ~100% electron injection efficiency in CdSe-QDSSCs36. When we add Li 2 S to the electrolyte at 50% methanol concentration, we do indeed observe an increase in J sc ; however, it is accompanied by a reduction in the V oc (Supplementary Fig.…”

“…The enhancement in the photocurrent however can be caused by several effects. In our studies, we have considered three possibilities: (1) methanol can potentially act as a sacrificial electron donor aiding in the reduction of photogenerated holes2627; (2) it could improve electron injection efficiency by lowering the Fermi level of the TiO 2 film36 and (3) it can lead to better contact between the QDs and the electrolyte due to improved wetting35.…”

Enhanced photoluminescence of water-soluble CdTe nanocrystals induced by light and pyridine

“…During the past decades, II-VI semiconductor nanocrystals have attracted extensive attentions because of their size-dependent physicochemical and optoelectronic properties, which result in exciting applications in optoelectronic [1], photovoltaic devices [2], bio-labeling [3] and so forth [4]. In particular, due to their superior properties of size-dependent emission, large extinction coefficients as well as excellent photostability over the fluorescent organic dyes, luminescent II-VI semiconductor nanocrystals are considered to be alternative candidates for use in light-emitting devices and tagging applications, thus have attracted increasing interests [3,5].…”

Layer‐by‐Layer Fabrication of Nanowire Sensitized Solar Cells: Geometry‐Independent Integration

“…[6][7][8] The in situ approach has generally afforded comparatively higher device effi ciencies, with the ex situ approach often suffering from lower nanocrystal loading and/or poor electronic coupling between the nanocrystals and the oxide due to the presence of intervening molecular 'ligands,' which are present on the nanocrystal surfaces. [ 9,10 ] However, the ex situ strategy offers in principle one distinct advantage -almost unlimited fl exibility in choice of semiconductor nanocrystal composition, size and morphology, where these characteristics can be used to fi nely tune semiconductor bandgap, exciton relaxation dynamics, electron-hole spatial separation, etc. In this way, the ability to address the nanocrystal loading and nanocrystal-oxide coupling issues currently limiting ex situ approaches remains an important challenge for optimizing NCSSC effi ciencies.…”