Built-in Quantum Dot Antennas in Dye-Sensitized Solar Cells

Abstract

A new design of dye-sensitized solar cells involves colloidal semiconductor quantum dots that serve as antennas, funneling absorbed light to the charge separating dye molecules via nonradiative energy transfer. The colloidal quantum dot donors are incorporated into the solid titania electrode resulting in high energy transfer efficiency and significant improvement of the cell stability. This design practically separates the processes of light absorption and charge carrier injection, enabling us to optimize each of these separately. Incident photon-to-current efficiency measurements show a full coverage of the visible spectrum despite the use of a red absorbing dye, limited only by the efficiency of charge injection from the dye to the titania electrode. Time resolved luminescence measurements clearly relate this to Forster resonance energy transfer from the quantum dots to the dye. The presented design introduces new degrees of freedom in the utilization of quantum dot sensitizers for photovoltaic cells. In particular, it opens the way toward the utilization of new materials whose band offsets do not allow direct charge injection.

Photonic effects on the Förster resonance energy transfer efficiency

“…The concept of ET from sensitizers such as colloidal semiconductor quantum dots [22][23][24] , dye molecules [25][26][27][28] or silicon NCs 29-31 is widely used. It can, for example, improve the spectral response of photovoltaic devices, increase the output of phosphors or optical amplifiers or be used for colour tuning in lighting.…”

Ultrafast characterization of the electron injection from CdSe quantum dots and dye N719 co-sensitizers into TiO2 using sulfide based ionic liquid for enhanced long term stability

“…8,9 In addition, semiconductor QDs are excellent building blocks for the design of light supracollecting structures by the synergetic combination of different types of QDs, 10,11 or QDs and dyes. [12][13][14][15][16][17][18][19][20] Different QDs and dye hybrid systems have been explored with the aim to exploit their interacting proprieties. In this heterostructures, performance can arise from the fast scavenging of photogenerated holes in quantum dots by a molecular dye.…”

“…15,19 Simultaneously, the combined use of QD and dye enhances the light harvesting wavelength range due to the combined absorption of the two assembled sensitizers. 12,17,18 Although hybrid sensitized systems appear promising, only few examples have been…”

Employing ZnS as a capping material for PbS quantum dots and bulk heterojunction solar cells

“…The spectra exhibit red shift with the deposition cycle, indicating gradually increased size as well as amount of the QDs. Considering the band alignment with reference to TiO2 substrates [20,21,32,33], five deposition cycles for PbS QDs were adopted in this study for efficient electron injection (smaller than 5.5 nm) [27,28]. In conventional colloidal QDs, organic molecules are used as the capping ligands to control the QD size.…”