The Renaissance of Iron Pyrite Photovoltaics: Progress, Challenges, and Perspectives - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 152

Fig. 12 J-V curve of pyrite/
platinum Schottky solar cell.
Reprinted with permission
from [ 57 ]
3.2 Pyrite Nanocrystal Photovoltaic Technology
The reason behind creating and controlling the shape of pyrite nanocrystals is to
ultimately use the material in useful devices. Most of the recent papers on syn-
thesis have also included attempts at creating working photovoltaic (PV) devices.
No attempt has yet been made to create devices out of the beautiful cubes that the
Stoldt group created. The Law group showed that after sintering the nanocrystal
films were no longer viable for PV applications due to the holes left over.
Steinhagen et al. has gone on to utilize pyrite nanocrystals much like the Law
group's in a battery of different PV architectures with no results [ 60 ]. Figure 14
shows all the different schematics that were tested. First a pure schottky barrier
device with gold and pyrite was tried. As seen, this device did not even show diode
behavior. Next a CuInSe 2 device was tested and showed a measly response of
0.03 mA/cm 2 short circuit current and 0.041 V open circuit voltage, resulting in a
negligible efficiency. A depleted heterojunction structure was also investigated by
putting a layer of pyrite on top of TiO 2 layer to act as a hole-blocking layer that
will limit recombination while simultaneously creating a depleted region. This
type of cell was recently shown to produce some of the highest efficiencies for
nanocrystal cells when utilizing lead sulfide [ 61 ]. When pyrite was used the cell
once again showed no performance. Finally, an organic/inorganic hybrid hetero-
junction was created. These devices have shown promise when coupling poly(3-
hexylthiophene) (P3HT), an organic polymer with other quantum dot systems [ 62 ].
When pyrite is tested, a V oc of 0.041 V and J sc of 0.007 mA/cm 2 was achieved,
once again showing an efficiency of zero. This communication was discouraging to
the hope of making use of pyrite's exceptional properties for solar devices, though
recently our group has made progress in creating working devices.
Our group took this valuable information from the Korgel report and examined
how we could work out the kinks in the pyrite system. The first thing that was
noted was that the type of crystals that was used was {111} terminated. As stated