Fabrication of three-dimensionally ordered macroporous TiO2 film and its application in quantum dots-sensitized solar cells

Engineering of TiO₂ photoanode is an important strategy for increasing the photovoltaic conversion efficiency of quantum dots-sensitized solar cells (QDSSCs). In this work, three-dimensional ordered macroporous (3DOM) TiO₂ films are fabricated by the controlled infiltrating-calcination method using the close-packed polystyrene spheres colloidal crystals as templates. The as-prepared macroporous TiO₂ films are then applied as the photoanode in colloidal CdSe QDSSCs. This structure not only facilitates the penetration of thioglycolic acid capped CdSe QDs, and thus achieving a high coverage of the internal surface with QDs sensitizer, but also exhibits a photonic band gap with tunable positions, which could enhance the light absorption. As a result, the liquid-junction QDSSCs assembled with the CdSe sensitized 3DOM TiO₂ yields a power conversion efficiency of 3.60% under solar illumination of 100 mW cm^-2, and this value is much higher than that of the device using nanoporous TiO₂ photoanode (1.82%). Our results indicate that the 3DOM TiO₂ is a promising candidate for the construction of high-efficiency QDSSCs.

Monolithic Two-Dimensional Photonic Crystal Reflectors for the Fabrication of Highly Efficient and Highly Transparent Dye-Sensitized Solar Cells

The transparent characteristic of dye-sensitized solar cells (DSCs) makes them suitable for building integrated photovoltaic (BIPV) devices. However, the diffusive scattering layer, which is usually used to increase the efficiency of these devices, greatly lowers the transparency of the DSC. This paper described a two-dimensional (2D) photonic crystal (PC) reflector with a sub-micrometer characteristic length that can improve the efficiency of these devices while maintaining transparency. This 2D PCs were fabricated directly onto TiO₂ photoelectrodes using colloidal lithography and have the structure of a nanopillar array. A nanopillar with a height of 430 nm was observed to selectively reflect up to 40% of the light of 400-500 nm wavelength. The perceived transparency of the 2D PC electrode was 52%, which is much higher than 0.3% of the conventional scattering layer. The DSC fabricated using the 2D PC electrode demonstrated a maximum photon-to-electric conversion efficiency of 8.23%, which is 18% higher than the pristine electrode. The 2D PC is a highly efficient and wavelength-selective reflector that can be applied to various photoelectric conversion devices.

A colloidoscope of colloid-based porous materials and their uses

Colloids assemble into a variety of bioinspired structures for applications including optics, wetting, sensing, catalysis, and electrodes.

N-doped mesoporous inverse opal structures for visible-light photocatalysts

N-doped, mesoporous IO TiO₂ structures were fabricated as visible-light photocatalysts.

Facile fabrication of sub-100 nm mesoscale inverse opal films and their application in dye-sensitized solar cell electrodes

Inverse opal (IO) films with mesoporous structures hold promise as high-performance electrodes for various photoelectrochemical devices because of their high specific area as well as their fully connected pore structure. A great challenge to their use is obtaining an intact film of mesoscale colloidal crystals as a template. Here, using the plate-sliding coating method coupled with hot air flow, we successfully deposited mesoscale colloidal crystals onto the substrate. A TiO₂ mesoscale IO (meso-IO) with 70 nm pores was then successfully fabricated via atomic layer deposition of TiO₂ and subsequent removal of the template. As a photoelectrochemical electrode, the meso-IO structure exhibits enhanced charge transport properties as well as a high specific area. Moreover, dye-sensitized solar cells fabricated using the meso-IO electrode exhibit a higher photocurrent and cell efficiency than a cell constructed using a conventional TiO₂ nanoparticle electrode. This meso-IO film provides a new platform for developing electrodes for use in various energy storage and conversion devices.

1D nanorod-planted 3D inverse opal structures for use in dye-sensitized solar cells

The effectiveness of the 1D nanorod (NR)-planted 3D inverse opal (IO) structure as an electrode for dye-sensitized solar cells (DSSCs) is demonstrated here. The NRs were grown on the surface of a macroporous IO structure and their longitudinal growth increased the surface area of the structure proportional to the growth duration. NR/IO electrodes with various NR growth times were compared. A remarkable JSC was obtained for the DSSCs utilizing a NR/IO electrode. The improvement of the JSC was analyzed in terms of its efficiency in light harvesting and electron transport. The growth of the NRs improved the dye adsorption density and scattering property of the electrode, resulting in an improvement in the light harvesting efficiency. Electrochemical impedance analysis revealed that the NRs also improved its electron transport properties. Further growth of the NRs tended to limit the increase of the JSC, which could be attributed to an overlap between them.