Quantum Dot Solar Cells. Tuning Photoresponse through Size and Shape Control of CdSe−TiO₂ Architecture

Abstract

Different-sized CdSe quantum dots have been assembled on TiO2 films composed of particle and nanotube morphologies using a bifunctional linker molecule. Upon band-gap excitation, CdSe quantum dots inject electrons into TiO2 nanoparticles and nanotubes, thus enabling the generation of photocurrent in a photoelectrochemical solar cell. The results presented in this study highlight two major findings: (i) ability to tune the photoelectrochemical response and photoconversion efficiency via size control of CdSe quantum dots and (ii) improvement in the photoconversion efficiency by facilitating the charge transport through TiO2 nanotube architecture. The maximum IPCE (photon-to-charge carrier generation efficiency) obtained with 3 nm diameter CdSe nanoparticles was 35% for particulate TiO2 and 45% for tubular TiO2 morphology. The maximum IPCE observed at the excitonic band increases with decreasing particle size, whereas the shift in the conduction band to more negative potentials increases the driving force and favors fast electron injection. The maximum power-conversion efficiency </=1% obtained with CdSe-TiO2 nanotube film highlights the usefulness of tubular morphology in facilitating charge transport in nanostructure-based solar cells. Ways to further improve power-conversion efficiency and maximize light-harvesting capability through the construction of a rainbow solar cell are discussed.

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

“…[1][2][3][4] Furthermore, the use of semiconductors as sensitizers has some unique advantages as the high extinction coefficients due to the quantum confinement, tunable band gap from the infra-red to the ultraviolet by adjusting the size, 5 large intrinsic dipole moments which may lead to a rapid charge separation, and the possibility of multiple electron generation (MEG) 6,7 which gives to QDSCs the capability to achieve quantum yields, or even external quantum efficiency, greater than 100%. 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.…”

Annealing Effect on Photovoltaic Performance of CdSe Quantum‐Dots‐Sensitized TiO2 Nanorod Solar Cells

“…An optical band gap of 2.04 eV is estimated for the as-synthesized CdSe nanoparticles from the absorption spectra, which are much Journal of Nanomaterials show an enhanced absorption in the visible range, which is very important for solar cell application and will result in higher power conversion efficiency. As shown by the XRD patterns, SEM images and HRTEM images, this red shift in the annealed samples could be explained by the annealing-induced phase transformation (from cubic to hexagonal) at the elevated temperatures as well as the increase in particle size [20]. The annealing effect on the optical absorption spectra of bare TiO 2 nanorod arrays was also studied.…”

Enhanced performance of solar cells via anchoring CuGaS2 quantum dots

“…The chalcopyrite semiconductor quantum dots (QDs), such as CdS(Se) [13][14][15][16][17][18][19][20], PbS(Se) [21][22][23][24], SnSe 2 [25], InAs [26,27], Sb 2 S 3 [28], were introduced into QDSSCs as light-harvesting sensitizers via various methods. Since photons with lower energy could be absorbed, the chalcopyrite semiconductor QDs are considered as a promising candidate for the high-efficiency solar cells [29].…”