光伏文献

liulisheng

顶顶顶顶New initiatives to harvest incident photons with greater
efficiency are needed to meet our demand of clean energy.1-4
The single crystal silicon based photovoltaic devices that are
commercially available for installation deliver power with a
～15% efficiency. These first generation devices suffer from
high cost of manufacturing and installation. The second generation
devices consisting of polycrystalline semiconductor thin
films can bring down the price significantly, but their efficiency
needs to be enhanced for making them practically viable. Now
the focus is on the third generation devices that can deliver
high efficiency devices at economically viable cost.
In recent years nanomaterials have emerged as the new
building blocks to construct light energy harvesting assemblies.
Efforts are being made to design organic and inorganic hybrid
structures that exhibit improved selectivity and efficiency toward
light energy conversion. Of particular interest are the size
dependent properties such as size quantization effects in
semiconductor nanoparticles and quantized charging effects in
metal nanoparticles.5-11 Recent efforts to synthesize nanostructures
with well defined geometrical shapes (e.g., solid and
hollow spheres, prisms, rods, tubes, and wires) and organize
them as 2- and 3-dimensional assemblies have further expanded
the possibility of developing new strategies for light energy
conversion.12-30
Quantum dot based solar cells have drawn a lot of attention
during past few years because of the possibility of boosting the
energy conversion efficiency beyond the traditional Shockley
and Queisser limit of 32% for Si based solar cells.31 Three
different types of solar cells that capitalize salient properties of
semiconductornanocrystalshaveemergedi)metal-semiconductor
or Schottky junction photovoltaic cell, (ii) semiconductor
nanostructure-polymer solar cell, and (iii) semiconductor sensitized
quantum dot solar cell (Figure 1).
Specific advantages to using semiconductor quantum dots as
light harvesting assemblies in solar cells exist.32 First and
foremost, their size quantization property allows one to tune
the visible response and vary the band offsets to modulate the
vectorial charge transfer across different sized particles.33 In
addition, these quantum dots open up new ways to utilize hot
electrons34 or generate multiple charge carriers with a single
photon.35,36 Multiple carrier generation in PbSe nanocrystals has
shown that two or more excitons can be generated with a single
photon of energy greater than the bandgap.35,37,38 These recent
developments of photoinduced charge separation semiconductor
nanocrystal based assemblies and efforts to utilize them in solar
cells are reviewed here.