Advanced Light Management in Solar Energy Conversion Devices
Event details
| Date | 23.11.2012 |
| Hour | 10:30 › 11:30 |
| Speaker | Dr. Fabio Di Fonzo, Istituto Italiano di Tecnologia, Milano |
| Location | |
| Category | Conferences - Seminars |
Controlling light is an essential requirement for devices aiming at capturing solar energy in order to produce electricity, like photovoltaics, or fuels, like hydrogen or simple hydrocarbons. Engineering light path with controlled light trapping strategies and orthogonalization of photon absorption and charge carrier transport pathways is of fundamental importance in order to increase efficiency in modern nanostructured systems. In this communication, we report on a novel fabrication method exploiting self-assembly from the gas-phase: Scattered Ballistic Deposition by Pulsed Laser Deposition (SBD-PLD). Pulsed Laser Deposition is a convenient, high throughput physical vapor technique that allows the generation of supersonic plasma jets from any inorganic material irrespective of melting temperature, preserving even the most complex stoichiometries. One of the advantages of PLD over other vapour deposition techniques is extremely wide operational pressure range, from UHV to ambient pressure. SBD is a general physical phenomenon that arises from the interaction of a supersonic molecular beam with an ambient gas and enables the growth of quasi-1D hierarchical mesostructures (HM). Overall, they resemble a forest composed of individual, high aspect-ratio, tree-like structures, assembled from crystalline nanoparticles. The hierarchical quasi-1D nature of each tree represents an innovative compromise between nanorods/nanotubes (better electron transport) and the conventional isotropic nanoparticle photoanode (high surface area). The so-fabricated Hierarchical Mesoporous Photoanodes (HMP) exhibit tunable properties controlled by deposition conditions and thermal treatments: high surface area (from 50 to 350 m2g-1); roughness factors up to 100; porosity and pore size distribution (5-20 nm); grain size (10-30 nm); refractive index (1.5-1.9); amorphous or anatase phase. In contrast to typical nanoparticle based mesoporous photoanodes (NMP), they are characterized by vertical channels through the entire thickness that assure excellent diffusional path for liquid electrolytes and easy infiltration for solid hole transporting materials. Optimized photoanodes show enhanced light trapping capabilities with high broadband scattering efficiency. Hence, upon sensitization of the transparent TiO2 HMP with visible light sensitive species, like dyes or Quantum Dots, they show increased optical density and broader absorption features with respect to standard NMP. These characteristics make the novel HMP ideal for solar capture and conversion technologies employing liquid or solid electrolytes. As an example, Solid State Dye Sensitized Solar Cells (SSDSC) fabricated with the novel hierarchical TiO2 photoanode show higher short circuit current, Jsc, in accordance to the higher optical density measured, and higher power conversion efficiency than conventional NMPs. A similar effect is obtained when the HMPs are used for hydrogen generation, upon sensitization with CdS QDs by the successive ionic layer adsorption and reaction (SILAR) technique. The as synthesized CdS/TiO2 electrodes showed higher photocurrent density than pure nanostructure TiO2 electrode and of CdS sensitized NMP.
In conclusion, HMP are a promising platform for next generation solar energy capture technologies offering new tools to confine light in active layers in order to enhance photocurrent generation and, in turn, conversion efficiency.
In conclusion, HMP are a promising platform for next generation solar energy capture technologies offering new tools to confine light in active layers in order to enhance photocurrent generation and, in turn, conversion efficiency.
Practical information
- General public
- Free
Organizer
- Morgan Stefik
Contact
- Morgan Stefik