The energy levels of CdS quantum dots (QDs) can be shifted in a systematic fashion with respect to the TiO(2) bands using molecular dipoles. Dipole moments pointing toward the QD surface shift the energy levels toward the vacuum level (a), thus enabling electron injection from excited QD states into the TiO(2) conduction band at lower photon energies compared to QDs with adsorbed molecular dipoles which are pointing away from the QD surface (b). In CdS QD sensitized solar cells this leads to a dipole dependent shift of the photovoltage onset and the photocurrent.

Here, we show that, in CdSe quantum dot sensitized solar cells (QDSCs), recombination of electrons from the transparent conducting oxide (TCO) front electrode with oxidized species of the polysulfide redox electrolyte cannot be neglected like in dye-sensitized solar cells (DSCs). We demonstrate that light to electric power conversion efficiencies up to 4% can be achieved when recombination at the front electrode is suppressed by a compact TiO 2 layer deposited in between the TCO substrate and the QD sensitized porous TiO 2 film. Numerical simulations based on a simple equivalent circuit suggest that, over a wide potential range, electron transfer into the electrolyte at the TCO substrate is the dominant recombination path, which is usually not considered, suggesting that the current understanding of QDSCs has to be revised.

A quantum dot sensitized solar cell based on a porous ZrO(2) film, sensitized with CdSe quantum dots using CdS as an intermediate layer is presented. We observe electron injection from photo-excited quantum dots into the ZrO(2), which is unexpected due to the much higher conduction band edge (closer to the vacuum level) of bulk ZrO(2) compared to TiO(2).

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We present results for dye sensitized solar cell (DSSC) electrodes based on high surface area indium tin oxide (ITO) coated with an active TiO2 layer. This design, denoted as a “collector‐shell electrode”, ensures a distance of several nanometers between the TiO2‐electrolyte interface and the current collector throughout the porous electrode, in contrast to several micrometers associated with the standard electrode. The new design also enables an inherent screening capability due to the high doping level of the conductive core matrix. Therefore, the importance of this electrode configuration is its ability to overcome the collection and image field problems in DSSCs, especially for solid‐state hole–conductor‐based devices. Efficiencies of 1.37% for cells containing ITO‐TiO2 collector‐shell electrodes and 1.63% for similar electrodes that received an additional coating of a thin MgO layer were achieved. We expect greater cell performance improvement after optimization of the nature and the size of conductive material particles, the TiO2 shell thickness and uniformity, and the barrier layer(s) properties.