Quantum dot-sensitized solar cells (QDSSCs) have attracted much attention in recent years because they have high theoretic light conversion efficiency, are cheap and are simple to make. However, compared with dye-sensitized solar cells (DSSCs), the solar-to-electric power conversion efficiencies of QDSSCs still remains low, something that has held back the mass production and more widespread use of these types of cells.

The team, led by Wei-Qiao Deng, synthesized Nb-doped anatase TiO2 nanocrystals prepared via a hydrothermal method and used this material as the photoelectrode in QDSSCs. This Nb doping significantly increases the electrical conductivity of the TiO22 nanocrystals and thus improves the collected photocurrent.

As shown in the figure, a solar cell with CdS/CdSe quantum dots co-sensitized with 2.5 mol% Nb-doped anatase TiO2 nanocrystals can achieve a photovoltaic conversion efficiency of 3.3%, which is almost twice as high as the 1.7% obtained in a cell based on undoped TiO2 nanocrystals. The incident photon-to-current conversion efficiency (IPCE) can reach as high as 91%, which is a record for QDSSCs. The as-prepared Nb-doped anatase TiO2 nanocrystals are better photoelectrode materials than pure TiO2 and this work provides a new way to improve the performance of QDSSCs.

We believe that further investigation into the effects of Nb doping will provide valuable insights into the design of high-performance QDSSCs and help in their mass production and more widespread application.

More information can be found in the journal Nanotechnology 24 415401.

Further reading

Plasmonics and quantum dots team up for solar harvesting (Sep 2013)
Quantum dot photonic nanocrystals increase conversion efficiency of solar cells (May 2012)
Quantum dots for highly efficient solar cells (Jun 2010)