The Renaissance of Iron Pyrite Photovoltaics: Progress, Challenges, and Perspectives - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 154

Fig. 14 J-V curves of all different pyrite solar cell schemes fabricated. Reprinted with

permission from [ 60 ]

strategy from organic PV systems was adapted; the bulk heterojunction. By mixing
the small CdS quantum dots with the bigger FeS 2 cubes and spincoating onto the
substrate a pseudo-bulk heterojunction was created. The CdS quantum dots created
a matrix around the bigger cubes that allowed for not only complete coverage of
the pyrite material, but also allowed for smooth films for electrodes to be deposited
onto. The band diagram, thin film absorption, and fluorescence quenching mea-
surements are shown in Fig. 15 . Absorption in the thin film showed absorption in
the NIR due to the cubes absorbance (see cube synthesis above). Fluorescence
quenching measurements showed that as the pyrite loading increased, better
quenching occurred, indicative of better exiton separation. Figure 16 shows TEM
images of the mixture of the CdS QDs and the FeS 2 cubes. The second image
shows the intimate contact of the QDs with the cubes edge that allows for
exceptional exiton splitting. The SEM image shows the cross-section of the active
layer, where the percolation of the cubes inside of the QD matrix can be seen. J-V
curves are presented in Fig. 17 . Three different loading ratios of Pyrite:CdS were
tested. The 1:1 (FeS 2 :CdS) ratio device preformed the best with average of J sc of
3.9 mA/cm 2 a V oc of 0.79 V and a fill factor of 0.36 giving it an over all efficiency