Researchers from the Dalian Institute of Chemical Physics in China have used niobium-doped titania nanocrystals as the photoanode material in quantum-dot-sensitized solar cells. The devices have a light conversion efficiency of 3.3%, a value that is almost twice as high as that possible with electrodes made from undoped titania nanocrystals, and the photon-to-current efficiency can reach 91%, which is a record for such cells.
A solar cell co-sensitized with Nb-doped anatase TiO22 nanocrystals
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.