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SUMMARY:Advanced Light Management in Solar Energy Conversion Devices
DTSTART:20121123T103000
DTEND:20121123T113000
DTSTAMP:20260925T120627Z
UID:9f124e178f45aa2e3a0a5462b81cbb3145cd3c637e75fd1307728f4c
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Fabio Di Fonzo\, Istituto Italiano di Tecnologia\, Milano\
 nControlling light is an essential requirement for devices aiming at captu
 ring solar energy in order to produce electricity\, like photovoltaics\, o
 r fuels\, like hydrogen or simple hydrocarbons. Engineering light path wit
 h controlled light trapping strategies and orthogonalization of photon abs
 orption 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-a
 ssembly from the gas-phase: Scattered Ballistic Deposition by Pulsed Laser
  Deposition (SBD-PLD). Pulsed Laser Deposition is a convenient\, high thro
 ughput physical vapor technique that allows the generation of supersonic p
 lasma 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 operatio
 nal pressure range\, from UHV to ambient pressure.   SBD is a general ph
 ysical phenomenon that arises from the interaction of a supersonic molecul
 ar beam with an ambient gas and enables the growth of quasi-1D hierarchica
 l mesostructures (HM). Overall\, they resemble a forest composed of indivi
 dual\, high aspect-ratio\, tree-like structures\, assembled from crystalli
 ne nanoparticles. The hierarchical quasi-1D nature of each tree represents
  an innovative compromise between nanorods/nanotubes (better electron tran
 sport) and the conventional isotropic nanoparticle photoanode (high surfac
 e area). The so-fabricated Hierarchical Mesoporous Photoanodes (HMP) exhib
 it tunable properties controlled by deposition conditions and thermal trea
 tments: 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 n
 m)\; refractive index (1.5-1.9)\; amorphous or anatase phase. In contrast 
 to typical nanoparticle based mesoporous photoanodes (NMP)\, they are char
 acterized by vertical channels through the entire thickness that assure ex
 cellent diffusional path for liquid electrolytes and easy infiltration for
  solid hole transporting materials. Optimized photoanodes show enhanced li
 ght trapping capabilities with high broadband scattering efficiency. Hence
 \, upon sensitization of the transparent TiO2 HMP with visible light sensi
 tive species\, like dyes or Quantum Dots\, they show increased optical den
 sity and broader absorption features with respect to standard NMP. These c
 haracteristics make the novel HMP ideal for solar capture and conversion t
 echnologies employing liquid or solid electrolytes. As an example\, Solid 
 State Dye Sensitized Solar Cells (SSDSC) fabricated with the novel hierarc
 hical TiO2 photoanode show higher short circuit current\, Jsc\, in accorda
 nce to the higher optical density measured\, and higher power conversion e
 fficiency than conventional NMPs. A similar effect is obtained when the HM
 Ps are used for hydrogen generation\, upon sensitization with CdS QDs by t
 he successive ionic layer adsorption and reaction (SILAR) technique. The a
 s synthesized CdS/TiO2 electrodes showed higher photocurrent density than 
 pure nanostructure TiO2 electrode and of CdS sensitized NMP.\nIn conclusio
 n\, 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.
LOCATION:CM1104 http://plan.epfl.ch/?lang=en&room=cm+1104
STATUS:CONFIRMED
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